76 files changed, 4595 insertions, 2010 deletions

diff --git a/crates/paths/Cargo.toml b/crates/paths/Cargo.toml
new file mode 100644
index 000000000..646ee7fd5
--- /dev/null
+++ b/crates/paths/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "paths"
+version = "0.1.0"
+authors = ["rust-analyzer developers"]
+edition = "2018"
+
+[lib]
+doctest = false
diff --git a/crates/paths/src/lib.rs b/crates/paths/src/lib.rs
new file mode 100644
index 000000000..190c50913
--- /dev/null
+++ b/crates/paths/src/lib.rs
@@ -0,0 +1,126 @@
+//! Thin wrappers around `std::path`, distinguishing between absolute and
+//! relative paths.
+use std::{
+    convert::{TryFrom, TryInto},
+    io, ops,
+    path::{Component, Path, PathBuf},
+};
+
+#[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct AbsPathBuf(PathBuf);
+
+impl From<AbsPathBuf> for PathBuf {
+    fn from(AbsPathBuf(path_buf): AbsPathBuf) -> PathBuf {
+        path_buf
+    }
+}
+
+impl ops::Deref for AbsPathBuf {
+    type Target = AbsPath;
+    fn deref(&self) -> &AbsPath {
+        self.as_path()
+    }
+}
+
+impl AsRef<Path> for AbsPathBuf {
+    fn as_ref(&self) -> &Path {
+        self.0.as_path()
+    }
+}
+
+impl TryFrom<PathBuf> for AbsPathBuf {
+    type Error = PathBuf;
+    fn try_from(path_buf: PathBuf) -> Result<AbsPathBuf, PathBuf> {
+        if !path_buf.is_absolute() {
+            return Err(path_buf);
+        }
+        Ok(AbsPathBuf(path_buf))
+    }
+}
+
+impl TryFrom<&str> for AbsPathBuf {
+    type Error = PathBuf;
+    fn try_from(path: &str) -> Result<AbsPathBuf, PathBuf> {
+        AbsPathBuf::try_from(PathBuf::from(path))
+    }
+}
+
+impl AbsPathBuf {
+    pub fn canonicalized(path: &Path) -> io::Result<AbsPathBuf> {
+        path.canonicalize().map(|it| AbsPathBuf::try_from(it).unwrap())
+    }
+    pub fn as_path(&self) -> &AbsPath {
+        AbsPath::new_unchecked(self.0.as_path())
+    }
+    pub fn pop(&mut self) -> bool {
+        self.0.pop()
+    }
+}
+
+#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash)]
+#[repr(transparent)]
+pub struct AbsPath(Path);
+
+impl ops::Deref for AbsPath {
+    type Target = Path;
+    fn deref(&self) -> &Path {
+        &self.0
+    }
+}
+
+impl AsRef<Path> for AbsPath {
+    fn as_ref(&self) -> &Path {
+        &self.0
+    }
+}
+
+impl<'a> TryFrom<&'a Path> for &'a AbsPath {
+    type Error = &'a Path;
+    fn try_from(path: &'a Path) -> Result<&'a AbsPath, &'a Path> {
+        if !path.is_absolute() {
+            return Err(path);
+        }
+        Ok(AbsPath::new_unchecked(path))
+    }
+}
+
+impl AbsPath {
+    fn new_unchecked(path: &Path) -> &AbsPath {
+        unsafe { &*(path as *const Path as *const AbsPath) }
+    }
+
+    pub fn join(&self, path: impl AsRef<Path>) -> AbsPathBuf {
+        self.as_ref().join(path).try_into().unwrap()
+    }
+    pub fn normalize(&self) -> AbsPathBuf {
+        AbsPathBuf(normalize_path(&self.0))
+    }
+}
+
+// https://github.com/rust-lang/cargo/blob/79c769c3d7b4c2cf6a93781575b7f592ef974255/src/cargo/util/paths.rs#L60-L85
+fn normalize_path(path: &Path) -> PathBuf {
+    let mut components = path.components().peekable();
+    let mut ret = if let Some(c @ Component::Prefix(..)) = components.peek().cloned() {
+        components.next();
+        PathBuf::from(c.as_os_str())
+    } else {
+        PathBuf::new()
+    };
+
+    for component in components {
+        match component {
+            Component::Prefix(..) => unreachable!(),
+            Component::RootDir => {
+                ret.push(component.as_os_str());
+            }
+            Component::CurDir => {}
+            Component::ParentDir => {
+                ret.pop();
+            }
+            Component::Normal(c) => {
+                ret.push(c);
+            }
+        }
+    }
+    ret
+}
diff --git a/crates/ra_assists/src/assist_context.rs b/crates/ra_assists/src/assist_context.rs
index edd8255f4..ee614de72 100644
--- a/crates/ra_assists/src/assist_context.rs
+++ b/crates/ra_assists/src/assist_context.rs
@@ -252,7 +252,7 @@ impl AssistBuilder {
     pub(crate) fn rewrite(&mut self, rewriter: SyntaxRewriter) {
         let node = rewriter.rewrite_root().unwrap();
         let new = rewriter.rewrite(&node);
-        algo::diff(&node, &new).into_text_edit(&mut self.edit)
+        algo::diff(&node, &new).into_text_edit(&mut self.edit);
     }
 
     // FIXME: kill this API
diff --git a/crates/ra_assists/src/ast_transform.rs b/crates/ra_assists/src/ast_transform.rs
index 3079a02a2..00fa95b6c 100644
--- a/crates/ra_assists/src/ast_transform.rs
+++ b/crates/ra_assists/src/ast_transform.rs
@@ -106,6 +106,7 @@ impl<'a> SubstituteTypeParams<'a> {
             _ => return None,
         };
         // FIXME: use `hir::Path::from_src` instead.
+        #[allow(deprecated)]
         let path = hir::Path::from_ast(path)?;
         let resolution = self.source_scope.resolve_hir_path(&path)?;
         match resolution {
@@ -150,6 +151,7 @@ impl<'a> QualifyPaths<'a> {
             return None;
         }
         // FIXME: use `hir::Path::from_src` instead.
+        #[allow(deprecated)]
         let hir_path = hir::Path::from_ast(p.clone());
         let resolution = self.source_scope.resolve_hir_path(&hir_path?)?;
         match resolution {
diff --git a/crates/ra_assists/src/handlers/fill_match_arms.rs b/crates/ra_assists/src/handlers/fill_match_arms.rs
index cc303285b..569efb768 100644
--- a/crates/ra_assists/src/handlers/fill_match_arms.rs
+++ b/crates/ra_assists/src/handlers/fill_match_arms.rs
@@ -136,8 +136,20 @@ fn is_variant_missing(existing_arms: &mut Vec<MatchArm>, var: &Pat) -> bool {
 }
 
 fn does_pat_match_variant(pat: &Pat, var: &Pat) -> bool {
-    let pat_head = pat.syntax().first_child().map(|node| node.text());
-    let var_head = var.syntax().first_child().map(|node| node.text());
+    let first_node_text = |pat: &Pat| pat.syntax().first_child().map(|node| node.text());
+
+    let pat_head = match pat {
+        Pat::BindPat(bind_pat) => {
+            if let Some(p) = bind_pat.pat() {
+                first_node_text(&p)
+            } else {
+                return false;
+            }
+        }
+        pat => first_node_text(pat),
+    };
+
+    let var_head = first_node_text(var);
 
     pat_head == var_head
 }
@@ -351,6 +363,40 @@ mod tests {
     }
 
     #[test]
+    fn partial_fill_bind_pat() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A {
+                As,
+                Bs,
+                Cs(Option<i32>),
+            }
+            fn main() {
+                match A::As<|> {
+                    A::As(_) => {}
+                    a @ A::Bs(_) => {}
+                }
+            }
+            "#,
+            r#"
+            enum A {
+                As,
+                Bs,
+                Cs(Option<i32>),
+            }
+            fn main() {
+                match A::As {
+                    A::As(_) => {}
+                    a @ A::Bs(_) => {}
+                    $0A::Cs(_) => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
     fn fill_match_arms_empty_body() {
         check_assist(
             fill_match_arms,
diff --git a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
index 0197a8cf0..b4784c333 100644
--- a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
+++ b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
@@ -1,7 +1,10 @@
 use hir;
-use ra_syntax::{ast, AstNode, SmolStr, TextRange};
+use ra_syntax::{algo::SyntaxRewriter, ast, match_ast, AstNode, SmolStr, SyntaxNode};
 
-use crate::{utils::insert_use_statement, AssistContext, AssistId, Assists};
+use crate::{
+    utils::{find_insert_use_container, insert_use_statement},
+    AssistContext, AssistId, Assists,
+};
 
 // Assist: replace_qualified_name_with_use
 //
@@ -39,16 +42,18 @@ pub(crate) fn replace_qualified_name_with_use(
         target,
         |builder| {
             let path_to_import = hir_path.mod_path().clone();
+            let container = match find_insert_use_container(path.syntax(), ctx) {
+                Some(c) => c,
+                None => return,
+            };
             insert_use_statement(path.syntax(), &path_to_import, ctx, builder.text_edit_builder());
 
-            if let Some(last) = path.segment() {
-                // Here we are assuming the assist will provide a correct use statement
-                // so we can delete the path qualifier
-                builder.delete(TextRange::new(
-                    path.syntax().text_range().start(),
-                    last.syntax().text_range().start(),
-                ));
-            }
+            // Now that we've brought the name into scope, re-qualify all paths that could be
+            // affected (that is, all paths inside the node we added the `use` to).
+            let mut rewriter = SyntaxRewriter::default();
+            let syntax = container.either(|l| l.syntax().clone(), |r| r.syntax().clone());
+            shorten_paths(&mut rewriter, syntax, path);
+            builder.rewrite(rewriter);
         },
     )
 }
@@ -73,6 +78,69 @@ fn collect_hir_path_segments(path: &hir::Path) -> Option<Vec<SmolStr>> {
     Some(ps)
 }
 
+/// Adds replacements to `re` that shorten `path` in all descendants of `node`.
+fn shorten_paths(rewriter: &mut SyntaxRewriter<'static>, node: SyntaxNode, path: ast::Path) {
+    for child in node.children() {
+        match_ast! {
+            match child {
+                // Don't modify `use` items, as this can break the `use` item when injecting a new
+                // import into the use tree.
+                ast::UseItem(_it) => continue,
+                // Don't descend into submodules, they don't have the same `use` items in scope.
+                ast::Module(_it) => continue,
+
+                ast::Path(p) => {
+                    match maybe_replace_path(rewriter, p.clone(), path.clone()) {
+                        Some(()) => {},
+                        None => shorten_paths(rewriter, p.syntax().clone(), path.clone()),
+                    }
+                },
+                _ => shorten_paths(rewriter, child, path.clone()),
+            }
+        }
+    }
+}
+
+fn maybe_replace_path(
+    rewriter: &mut SyntaxRewriter<'static>,
+    path: ast::Path,
+    target: ast::Path,
+) -> Option<()> {
+    if !path_eq(path.clone(), target.clone()) {
+        return None;
+    }
+
+    // Shorten `path`, leaving only its last segment.
+    if let Some(parent) = path.qualifier() {
+        rewriter.delete(parent.syntax());
+    }
+    if let Some(double_colon) = path.coloncolon_token() {
+        rewriter.delete(&double_colon);
+    }
+
+    Some(())
+}
+
+fn path_eq(lhs: ast::Path, rhs: ast::Path) -> bool {
+    let mut lhs_curr = lhs;
+    let mut rhs_curr = rhs;
+    loop {
+        match (lhs_curr.segment(), rhs_curr.segment()) {
+            (Some(lhs), Some(rhs)) if lhs.syntax().text() == rhs.syntax().text() => (),
+            _ => return false,
+        }
+
+        match (lhs_curr.qualifier(), rhs_curr.qualifier()) {
+            (Some(lhs), Some(rhs)) => {
+                lhs_curr = lhs;
+                rhs_curr = rhs;
+            }
+            (None, None) => return true,
+            _ => return false,
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::tests::{check_assist, check_assist_not_applicable};
@@ -83,10 +151,10 @@ mod tests {
     fn test_replace_add_use_no_anchor() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 std::fmt::Debug<|>
     ",
-            "
+            r"
 use std::fmt::Debug;
 
 Debug
@@ -97,13 +165,13 @@ Debug
     fn test_replace_add_use_no_anchor_with_item_below() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 std::fmt::Debug<|>
 
 fn main() {
 }
     ",
-            "
+            r"
 use std::fmt::Debug;
 
 Debug
@@ -118,13 +186,13 @@ fn main() {
     fn test_replace_add_use_no_anchor_with_item_above() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 fn main() {
 }
 
 std::fmt::Debug<|>
     ",
-            "
+            r"
 use std::fmt::Debug;
 
 fn main() {
@@ -139,10 +207,10 @@ Debug
     fn test_replace_add_use_no_anchor_2seg() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 std::fmt<|>::Debug
     ",
-            "
+            r"
 use std::fmt;
 
 fmt::Debug
@@ -154,13 +222,13 @@ fmt::Debug
     fn test_replace_add_use() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use stdx;
 
 impl std::fmt::Debug<|> for Foo {
 }
     ",
-            "
+            r"
 use stdx;
 use std::fmt::Debug;
 
@@ -174,11 +242,11 @@ impl Debug for Foo {
     fn test_replace_file_use_other_anchor() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 impl std::fmt::Debug<|> for Foo {
 }
     ",
-            "
+            r"
 use std::fmt::Debug;
 
 impl Debug for Foo {
@@ -191,11 +259,11 @@ impl Debug for Foo {
     fn test_replace_add_use_other_anchor_indent() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
     impl std::fmt::Debug<|> for Foo {
     }
     ",
-            "
+            r"
     use std::fmt::Debug;
 
     impl Debug for Foo {
@@ -208,13 +276,13 @@ impl Debug for Foo {
     fn test_replace_split_different() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt;
 
 impl std::io<|> for Foo {
 }
     ",
-            "
+            r"
 use std::{io, fmt};
 
 impl io for Foo {
@@ -227,13 +295,13 @@ impl io for Foo {
     fn test_replace_split_self_for_use() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt;
 
 impl std::fmt::Debug<|> for Foo {
 }
     ",
-            "
+            r"
 use std::fmt::{self, Debug, };
 
 impl Debug for Foo {
@@ -246,13 +314,13 @@ impl Debug for Foo {
     fn test_replace_split_self_for_target() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt::Debug;
 
 impl std::fmt<|> for Foo {
 }
     ",
-            "
+            r"
 use std::fmt::{self, Debug};
 
 impl fmt for Foo {
@@ -265,13 +333,13 @@ impl fmt for Foo {
     fn test_replace_add_to_nested_self_nested() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt::{Debug, nested::{Display}};
 
 impl std::fmt::nested<|> for Foo {
 }
 ",
-            "
+            r"
 use std::fmt::{Debug, nested::{Display, self}};
 
 impl nested for Foo {
@@ -284,13 +352,13 @@ impl nested for Foo {
     fn test_replace_add_to_nested_self_already_included() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt::{Debug, nested::{self, Display}};
 
 impl std::fmt::nested<|> for Foo {
 }
 ",
-            "
+            r"
 use std::fmt::{Debug, nested::{self, Display}};
 
 impl nested for Foo {
@@ -303,13 +371,13 @@ impl nested for Foo {
     fn test_replace_add_to_nested_nested() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt::{Debug, nested::{Display}};
 
 impl std::fmt::nested::Debug<|> for Foo {
 }
 ",
-            "
+            r"
 use std::fmt::{Debug, nested::{Display, Debug}};
 
 impl Debug for Foo {
@@ -322,13 +390,13 @@ impl Debug for Foo {
     fn test_replace_split_common_target_longer() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt::Debug;
 
 impl std::fmt::nested::Display<|> for Foo {
 }
 ",
-            "
+            r"
 use std::fmt::{nested::Display, Debug};
 
 impl Display for Foo {
@@ -341,13 +409,13 @@ impl Display for Foo {
     fn test_replace_split_common_use_longer() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt::nested::Debug;
 
 impl std::fmt::Display<|> for Foo {
 }
 ",
-            "
+            r"
 use std::fmt::{Display, nested::Debug};
 
 impl Display for Foo {
@@ -360,7 +428,7 @@ impl Display for Foo {
     fn test_replace_use_nested_import() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use crate::{
     ty::{Substs, Ty},
     AssocItem,
@@ -368,7 +436,7 @@ use crate::{
 
 fn foo() { crate::ty::lower<|>::trait_env() }
 ",
-            "
+            r"
 use crate::{
     ty::{Substs, Ty, lower},
     AssocItem,
@@ -383,13 +451,13 @@ fn foo() { lower::trait_env() }
     fn test_replace_alias() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt as foo;
 
 impl foo::Debug<|> for Foo {
 }
 ",
-            "
+            r"
 use std::fmt as foo;
 
 impl Debug for Foo {
@@ -402,7 +470,7 @@ impl Debug for Foo {
     fn test_replace_not_applicable_one_segment() {
         check_assist_not_applicable(
             replace_qualified_name_with_use,
-            "
+            r"
 impl foo<|> for Foo {
 }
 ",
@@ -413,7 +481,7 @@ impl foo<|> for Foo {
     fn test_replace_not_applicable_in_use() {
         check_assist_not_applicable(
             replace_qualified_name_with_use,
-            "
+            r"
 use std::fmt<|>;
 ",
         );
@@ -423,14 +491,14 @@ use std::fmt<|>;
     fn test_replace_add_use_no_anchor_in_mod_mod() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 mod foo {
     mod bar {
         std::fmt::Debug<|>
     }
 }
     ",
-            "
+            r"
 mod foo {
     mod bar {
         use std::fmt::Debug;
@@ -446,14 +514,14 @@ mod foo {
     fn inserts_imports_after_inner_attributes() {
         check_assist(
             replace_qualified_name_with_use,
-            "
+            r"
 #![allow(dead_code)]
 
 fn main() {
     std::fmt::Debug<|>
 }
     ",
-            "
+            r"
 #![allow(dead_code)]
 use std::fmt::Debug;
 
@@ -463,4 +531,116 @@ fn main() {
     ",
         );
     }
+
+    #[test]
+    fn replaces_all_affected_paths() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+fn main() {
+    std::fmt::Debug<|>;
+    let x: std::fmt::Debug = std::fmt::Debug;
+}
+    ",
+            r"
+use std::fmt::Debug;
+
+fn main() {
+    Debug;
+    let x: Debug = Debug;
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn replaces_all_affected_paths_mod() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+mod m {
+    fn f() {
+        std::fmt::Debug<|>;
+        let x: std::fmt::Debug = std::fmt::Debug;
+    }
+    fn g() {
+        std::fmt::Debug;
+    }
+}
+
+fn f() {
+    std::fmt::Debug;
+}
+    ",
+            r"
+mod m {
+    use std::fmt::Debug;
+
+    fn f() {
+        Debug;
+        let x: Debug = Debug;
+    }
+    fn g() {
+        Debug;
+    }
+}
+
+fn f() {
+    std::fmt::Debug;
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn does_not_replace_in_submodules() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+fn main() {
+    std::fmt::Debug<|>;
+}
+
+mod sub {
+    fn f() {
+        std::fmt::Debug;
+    }
+}
+    ",
+            r"
+use std::fmt::Debug;
+
+fn main() {
+    Debug;
+}
+
+mod sub {
+    fn f() {
+        std::fmt::Debug;
+    }
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn does_not_replace_in_use() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt::Display;
+
+fn main() {
+    std::fmt<|>;
+}
+    ",
+            r"
+use std::fmt::{self, Display};
+
+fn main() {
+    fmt;
+}
+    ",
+        );
+    }
 }
diff --git a/crates/ra_assists/src/utils.rs b/crates/ra_assists/src/utils.rs
index 0038a9764..c1ff0de7b 100644
--- a/crates/ra_assists/src/utils.rs
+++ b/crates/ra_assists/src/utils.rs
@@ -13,7 +13,7 @@ use rustc_hash::FxHashSet;
 
 use crate::assist_config::SnippetCap;
 
-pub(crate) use insert_use::insert_use_statement;
+pub(crate) use insert_use::{find_insert_use_container, insert_use_statement};
 
 #[derive(Clone, Copy, Debug)]
 pub(crate) enum Cursor<'a> {
diff --git a/crates/ra_assists/src/utils/insert_use.rs b/crates/ra_assists/src/utils/insert_use.rs
index 0ee43482f..8c4f33e59 100644
--- a/crates/ra_assists/src/utils/insert_use.rs
+++ b/crates/ra_assists/src/utils/insert_use.rs
@@ -12,6 +12,20 @@ use ra_syntax::{
 use ra_text_edit::TextEditBuilder;
 
 use crate::assist_context::AssistContext;
+use either::Either;
+
+/// Determines the containing syntax node in which to insert a `use` statement affecting `position`.
+pub(crate) fn find_insert_use_container(
+    position: &SyntaxNode,
+    ctx: &AssistContext,
+) -> Option<Either<ast::ItemList, ast::SourceFile>> {
+    ctx.sema.ancestors_with_macros(position.clone()).find_map(|n| {
+        if let Some(module) = ast::Module::cast(n.clone()) {
+            return module.item_list().map(|it| Either::Left(it));
+        }
+        Some(Either::Right(ast::SourceFile::cast(n)?))
+    })
+}
 
 /// Creates and inserts a use statement for the given path to import.
 /// The use statement is inserted in the scope most appropriate to the
@@ -24,15 +38,11 @@ pub(crate) fn insert_use_statement(
     builder: &mut TextEditBuilder,
 ) {
     let target = path_to_import.to_string().split("::").map(SmolStr::new).collect::<Vec<_>>();
-    let container = ctx.sema.ancestors_with_macros(position.clone()).find_map(|n| {
-        if let Some(module) = ast::Module::cast(n.clone()) {
-            return module.item_list().map(|it| it.syntax().clone());
-        }
-        ast::SourceFile::cast(n).map(|it| it.syntax().clone())
-    });
+    let container = find_insert_use_container(position, ctx);
 
     if let Some(container) = container {
-        let action = best_action_for_target(container, position.clone(), &target);
+        let syntax = container.either(|l| l.syntax().clone(), |r| r.syntax().clone());
+        let action = best_action_for_target(syntax, position.clone(), &target);
         make_assist(&action, &target, builder);
     }
 }
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 1a9f6cc76..ffd5278ec 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -26,8 +26,8 @@ use hir_ty::{
     autoderef,
     display::{HirDisplayError, HirFormatter},
     expr::ExprValidator,
-    method_resolution, ApplicationTy, Canonical, InEnvironment, Substs, TraitEnvironment, Ty,
-    TyDefId, TypeCtor,
+    method_resolution, ApplicationTy, Canonical, GenericPredicate, InEnvironment, Substs,
+    TraitEnvironment, Ty, TyDefId, TypeCtor,
 };
 use ra_db::{CrateId, CrateName, Edition, FileId};
 use ra_prof::profile;
@@ -186,6 +186,22 @@ impl ModuleDef {
 
         module.visibility_of(db, self)
     }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        match self {
+            ModuleDef::Adt(it) => Some(it.name(db)),
+            ModuleDef::Trait(it) => Some(it.name(db)),
+            ModuleDef::Function(it) => Some(it.name(db)),
+            ModuleDef::EnumVariant(it) => Some(it.name(db)),
+            ModuleDef::TypeAlias(it) => Some(it.name(db)),
+
+            ModuleDef::Module(it) => it.name(db),
+            ModuleDef::Const(it) => it.name(db),
+            ModuleDef::Static(it) => it.name(db),
+
+            ModuleDef::BuiltinType(it) => Some(it.as_name()),
+        }
+    }
 }
 
 pub use hir_def::{
@@ -1359,6 +1375,27 @@ impl Type {
         Some(adt.into())
     }
 
+    pub fn as_dyn_trait(&self) -> Option<Trait> {
+        self.ty.value.dyn_trait().map(Into::into)
+    }
+
+    pub fn as_impl_traits(&self, db: &dyn HirDatabase) -> Option<Vec<Trait>> {
+        self.ty.value.impl_trait_bounds(db).map(|it| {
+            it.into_iter()
+                .filter_map(|pred| match pred {
+                    hir_ty::GenericPredicate::Implemented(trait_ref) => {
+                        Some(Trait::from(trait_ref.trait_))
+                    }
+                    _ => None,
+                })
+                .collect()
+        })
+    }
+
+    pub fn as_associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<Trait> {
+        self.ty.value.associated_type_parent_trait(db).map(Into::into)
+    }
+
     // FIXME: provide required accessors such that it becomes implementable from outside.
     pub fn is_equal_for_find_impls(&self, other: &Type) -> bool {
         match (&self.ty.value, &other.ty.value) {
@@ -1380,6 +1417,80 @@ impl Type {
             ty: InEnvironment { value: ty, environment: self.ty.environment.clone() },
         }
     }
+
+    pub fn walk(&self, db: &dyn HirDatabase, mut cb: impl FnMut(Type)) {
+        // TypeWalk::walk for a Ty at first visits parameters and only after that the Ty itself.
+        // We need a different order here.
+
+        fn walk_substs(
+            db: &dyn HirDatabase,
+            type_: &Type,
+            substs: &Substs,
+            cb: &mut impl FnMut(Type),
+        ) {
+            for ty in substs.iter() {
+                walk_type(db, &type_.derived(ty.clone()), cb);
+            }
+        }
+
+        fn walk_bounds(
+            db: &dyn HirDatabase,
+            type_: &Type,
+            bounds: &[GenericPredicate],
+            cb: &mut impl FnMut(Type),
+        ) {
+            for pred in bounds {
+                match pred {
+                    GenericPredicate::Implemented(trait_ref) => {
+                        cb(type_.clone());
+                        walk_substs(db, type_, &trait_ref.substs, cb);
+                    }
+                    _ => (),
+                }
+            }
+        }
+
+        fn walk_type(db: &dyn HirDatabase, type_: &Type, cb: &mut impl FnMut(Type)) {
+            let ty = type_.ty.value.strip_references();
+            match ty {
+                Ty::Apply(ApplicationTy { ctor, parameters }) => {
+                    match ctor {
+                        TypeCtor::Adt(_) => {
+                            cb(type_.derived(ty.clone()));
+                        }
+                        TypeCtor::AssociatedType(_) => {
+                            if let Some(_) = ty.associated_type_parent_trait(db) {
+                                cb(type_.derived(ty.clone()));
+                            }
+                        }
+                        _ => (),
+                    }
+
+                    // adt params, tuples, etc...
+                    walk_substs(db, type_, parameters, cb);
+                }
+                Ty::Opaque(opaque_ty) => {
+                    if let Some(bounds) = ty.impl_trait_bounds(db) {
+                        walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
+                    }
+
+                    walk_substs(db, type_, &opaque_ty.parameters, cb);
+                }
+                Ty::Placeholder(_) => {
+                    if let Some(bounds) = ty.impl_trait_bounds(db) {
+                        walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
+                    }
+                }
+                Ty::Dyn(bounds) => {
+                    walk_bounds(db, &type_.derived(ty.clone()), bounds.as_ref(), cb);
+                }
+
+                _ => (),
+            }
+        }
+
+        walk_type(db, self, &mut cb);
+    }
 }
 
 impl HirDisplay for Type {
diff --git a/crates/ra_hir_def/src/diagnostics.rs b/crates/ra_hir_def/src/diagnostics.rs
index 510c5e064..30db48f86 100644
--- a/crates/ra_hir_def/src/diagnostics.rs
+++ b/crates/ra_hir_def/src/diagnostics.rs
@@ -3,7 +3,6 @@
 use std::any::Any;
 
 use hir_expand::diagnostics::Diagnostic;
-use ra_db::RelativePathBuf;
 use ra_syntax::{ast, AstPtr, SyntaxNodePtr};
 
 use hir_expand::{HirFileId, InFile};
@@ -12,7 +11,7 @@ use hir_expand::{HirFileId, InFile};
 pub struct UnresolvedModule {
     pub file: HirFileId,
     pub decl: AstPtr<ast::Module>,
-    pub candidate: RelativePathBuf,
+    pub candidate: String,
 }
 
 impl Diagnostic for UnresolvedModule {
diff --git a/crates/ra_hir_def/src/nameres.rs b/crates/ra_hir_def/src/nameres.rs
index f279c2ad4..b8560fdc9 100644
--- a/crates/ra_hir_def/src/nameres.rs
+++ b/crates/ra_hir_def/src/nameres.rs
@@ -119,13 +119,6 @@ impl Default for ModuleOrigin {
 }
 
 impl ModuleOrigin {
-    pub(crate) fn not_sure_file(file: Option<FileId>, declaration: AstId<ast::Module>) -> Self {
-        match file {
-            None => ModuleOrigin::Inline { definition: declaration },
-            Some(definition) => ModuleOrigin::File { declaration, definition },
-        }
-    }
-
     fn declaration(&self) -> Option<AstId<ast::Module>> {
         match self {
             ModuleOrigin::File { declaration: module, .. }
@@ -296,7 +289,6 @@ pub enum ModuleSource {
 
 mod diagnostics {
     use hir_expand::diagnostics::DiagnosticSink;
-    use ra_db::RelativePathBuf;
     use ra_syntax::{ast, AstPtr};
 
     use crate::{db::DefDatabase, diagnostics::UnresolvedModule, nameres::LocalModuleId, AstId};
@@ -306,7 +298,7 @@ mod diagnostics {
         UnresolvedModule {
             module: LocalModuleId,
             declaration: AstId<ast::Module>,
-            candidate: RelativePathBuf,
+            candidate: String,
         },
     }
 
diff --git a/crates/ra_hir_def/src/nameres/collector.rs b/crates/ra_hir_def/src/nameres/collector.rs
index 976e5e585..77baa4c69 100644
--- a/crates/ra_hir_def/src/nameres/collector.rs
+++ b/crates/ra_hir_def/src/nameres/collector.rs
@@ -825,7 +825,10 @@ impl ModCollector<'_, '_> {
         let modules = &mut self.def_collector.def_map.modules;
         let res = modules.alloc(ModuleData::default());
         modules[res].parent = Some(self.module_id);
-        modules[res].origin = ModuleOrigin::not_sure_file(definition, declaration);
+        modules[res].origin = match definition {
+            None => ModuleOrigin::Inline { definition: declaration },
+            Some(definition) => ModuleOrigin::File { declaration, definition },
+        };
         for (name, mac) in modules[self.module_id].scope.collect_legacy_macros() {
             modules[res].scope.define_legacy_macro(name, mac)
         }
diff --git a/crates/ra_hir_def/src/nameres/mod_resolution.rs b/crates/ra_hir_def/src/nameres/mod_resolution.rs
index cede4a6fc..19fe0615a 100644
--- a/crates/ra_hir_def/src/nameres/mod_resolution.rs
+++ b/crates/ra_hir_def/src/nameres/mod_resolution.rs
@@ -44,7 +44,7 @@ impl ModDir {
         file_id: HirFileId,
         name: &Name,
         attr_path: Option<&SmolStr>,
-    ) -> Result<(FileId, ModDir), RelativePathBuf> {
+    ) -> Result<(FileId, ModDir), String> {
         let file_id = file_id.original_file(db.upcast());
 
         let mut candidate_files = Vec::new();
@@ -52,11 +52,11 @@ impl ModDir {
             Some(attr_path) => {
                 let base =
                     if self.root_non_dir_owner { self.path.parent().unwrap() } else { &self.path };
-                candidate_files.push(base.join(attr_path))
+                candidate_files.push(base.join(attr_path).to_string())
             }
             None => {
-                candidate_files.push(self.path.join(&format!("{}.rs", name)));
-                candidate_files.push(self.path.join(&format!("{}/mod.rs", name)));
+                candidate_files.push(self.path.join(&format!("{}.rs", name)).to_string());
+                candidate_files.push(self.path.join(&format!("{}/mod.rs", name)).to_string());
             }
         };
 
diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
index ba16442bd..190d6d98d 100644
--- a/crates/ra_hir_def/src/path.rs
+++ b/crates/ra_hir_def/src/path.rs
@@ -154,7 +154,7 @@ pub enum GenericArg {
 
 impl Path {
     /// Converts an `ast::Path` to `Path`. Works with use trees.
-    /// DEPRECATED: It does not handle `$crate` from macro call.
+    #[deprecated = "Doesn't handle hygiene, don't add new calls, remove old ones"]
     pub fn from_ast(path: ast::Path) -> Option<Path> {
         lower::lower_path(path, &Hygiene::new_unhygienic())
     }
diff --git a/crates/ra_hir_ty/src/_match.rs b/crates/ra_hir_ty/src/_match.rs
index 3e6e1e333..5495ce284 100644
--- a/crates/ra_hir_ty/src/_match.rs
+++ b/crates/ra_hir_ty/src/_match.rs
@@ -8,11 +8,11 @@
 //! This file includes the logic for exhaustiveness and usefulness checking for
 //! pattern-matching. Specifically, given a list of patterns for a type, we can
 //! tell whether:
-//! (a) the patterns cover every possible constructor for the type [exhaustiveness]
-//! (b) each pattern is necessary [usefulness]
+//! - (a) the patterns cover every possible constructor for the type (exhaustiveness).
+//! - (b) each pattern is necessary (usefulness).
 //!
-//! The algorithm implemented here is a modified version of the one described in:
-//! http://moscova.inria.fr/~maranget/papers/warn/index.html
+//! The algorithm implemented here is a modified version of the one described in
+//! <http://moscova.inria.fr/~maranget/papers/warn/index.html>.
 //! However, to save future implementors from reading the original paper, we
 //! summarise the algorithm here to hopefully save time and be a little clearer
 //! (without being so rigorous).
@@ -37,20 +37,26 @@
 //! new pattern `p`.
 //!
 //! For example, say we have the following:
+//!
+//! ```ignore
+//! // x: (Option<bool>, Result<()>)
+//! match x {
+//!     (Some(true), _) => {}
+//!     (None, Err(())) => {}
+//!     (None, Err(_)) => {}
+//! }
 //! ```
-//!     // x: (Option<bool>, Result<()>)
-//!     match x {
-//!         (Some(true), _) => {}
-//!         (None, Err(())) => {}
-//!         (None, Err(_)) => {}
-//!     }
-//! ```
+//!
 //! Here, the matrix `P` starts as:
+//!
+//! ```text
 //! [
 //!     [(Some(true), _)],
 //!     [(None, Err(()))],
 //!     [(None, Err(_))],
 //! ]
+//! ```
+//!
 //! We can tell it's not exhaustive, because `U(P, _)` is true (we're not covering
 //! `[(Some(false), _)]`, for instance). In addition, row 3 is not useful, because
 //! all the values it covers are already covered by row 2.
@@ -60,53 +66,61 @@
 //! To match the paper, the top of the stack is at the beginning / on the left.
 //!
 //! There are two important operations on pattern-stacks necessary to understand the algorithm:
-//!     1. We can pop a given constructor off the top of a stack. This operation is called
-//!        `specialize`, and is denoted `S(c, p)` where `c` is a constructor (like `Some` or
-//!        `None`) and `p` a pattern-stack.
-//!        If the pattern on top of the stack can cover `c`, this removes the constructor and
-//!        pushes its arguments onto the stack. It also expands OR-patterns into distinct patterns.
-//!        Otherwise the pattern-stack is discarded.
-//!        This essentially filters those pattern-stacks whose top covers the constructor `c` and
-//!        discards the others.
 //!
-//!        For example, the first pattern above initially gives a stack `[(Some(true), _)]`. If we
-//!        pop the tuple constructor, we are left with `[Some(true), _]`, and if we then pop the
-//!        `Some` constructor we get `[true, _]`. If we had popped `None` instead, we would get
-//!        nothing back.
+//! 1. We can pop a given constructor off the top of a stack. This operation is called
+//!    `specialize`, and is denoted `S(c, p)` where `c` is a constructor (like `Some` or
+//!    `None`) and `p` a pattern-stack.
+//!    If the pattern on top of the stack can cover `c`, this removes the constructor and
+//!    pushes its arguments onto the stack. It also expands OR-patterns into distinct patterns.
+//!    Otherwise the pattern-stack is discarded.
+//!    This essentially filters those pattern-stacks whose top covers the constructor `c` and
+//!    discards the others.
+//!
+//!    For example, the first pattern above initially gives a stack `[(Some(true), _)]`. If we
+//!    pop the tuple constructor, we are left with `[Some(true), _]`, and if we then pop the
+//!    `Some` constructor we get `[true, _]`. If we had popped `None` instead, we would get
+//!    nothing back.
+//!
+//!    This returns zero or more new pattern-stacks, as follows. We look at the pattern `p_1`
+//!    on top of the stack, and we have four cases:
+//!
+//!    * 1.1. `p_1 = c(r_1, .., r_a)`, i.e. the top of the stack has constructor `c`. We push onto
+//!           the stack the arguments of this constructor, and return the result:
+//!
+//!          r_1, .., r_a, p_2, .., p_n
 //!
-//!        This returns zero or more new pattern-stacks, as follows. We look at the pattern `p_1`
-//!        on top of the stack, and we have four cases:
-//!             1.1. `p_1 = c(r_1, .., r_a)`, i.e. the top of the stack has constructor `c`. We
-//!                  push onto the stack the arguments of this constructor, and return the result:
-//!                     r_1, .., r_a, p_2, .., p_n
-//!             1.2. `p_1 = c'(r_1, .., r_a')` where `c ≠ c'`. We discard the current stack and
-//!                  return nothing.
-//!             1.3. `p_1 = _`. We push onto the stack as many wildcards as the constructor `c` has
-//!                  arguments (its arity), and return the resulting stack:
-//!                     _, .., _, p_2, .., p_n
-//!             1.4. `p_1 = r_1 | r_2`. We expand the OR-pattern and then recurse on each resulting
-//!                  stack:
-//!                     S(c, (r_1, p_2, .., p_n))
-//!                     S(c, (r_2, p_2, .., p_n))
+//!    * 1.2. `p_1 = c'(r_1, .., r_a')` where `c ≠ c'`. We discard the current stack and return
+//!           nothing.
+//!    * 1.3. `p_1 = _`. We push onto the stack as many wildcards as the constructor `c` has
+//!           arguments (its arity), and return the resulting stack:
 //!
-//!     2. We can pop a wildcard off the top of the stack. This is called `D(p)`, where `p` is
-//!        a pattern-stack.
-//!        This is used when we know there are missing constructor cases, but there might be
-//!        existing wildcard patterns, so to check the usefulness of the matrix, we have to check
-//!        all its *other* components.
+//!          _, .., _, p_2, .., p_n
 //!
-//!        It is computed as follows. We look at the pattern `p_1` on top of the stack,
-//!        and we have three cases:
-//!             1.1. `p_1 = c(r_1, .., r_a)`. We discard the current stack and return nothing.
-//!             1.2. `p_1 = _`. We return the rest of the stack:
-//!                     p_2, .., p_n
-//!             1.3. `p_1 = r_1 | r_2`. We expand the OR-pattern and then recurse on each resulting
-//!               stack.
-//!                     D((r_1, p_2, .., p_n))
-//!                     D((r_2, p_2, .., p_n))
+//!    * 1.4. `p_1 = r_1 | r_2`. We expand the OR-pattern and then recurse on each resulting stack:
 //!
-//!     Note that the OR-patterns are not always used directly in Rust, but are used to derive the
-//!     exhaustive integer matching rules, so they're written here for posterity.
+//!          S(c, (r_1, p_2, .., p_n))
+//!          S(c, (r_2, p_2, .., p_n))
+//!
+//! 2. We can pop a wildcard off the top of the stack. This is called `D(p)`, where `p` is
+//!    a pattern-stack.
+//!    This is used when we know there are missing constructor cases, but there might be
+//!    existing wildcard patterns, so to check the usefulness of the matrix, we have to check
+//!    all its *other* components.
+//!
+//!    It is computed as follows. We look at the pattern `p_1` on top of the stack,
+//!    and we have three cases:
+//!    * 1.1. `p_1 = c(r_1, .., r_a)`. We discard the current stack and return nothing.
+//!    * 1.2. `p_1 = _`. We return the rest of the stack:
+//!
+//!          p_2, .., p_n
+//!
+//!    * 1.3. `p_1 = r_1 | r_2`. We expand the OR-pattern and then recurse on each resulting stack:
+//!
+//!          D((r_1, p_2, .., p_n))
+//!          D((r_2, p_2, .., p_n))
+//!
+//!    Note that the OR-patterns are not always used directly in Rust, but are used to derive the
+//!    exhaustive integer matching rules, so they're written here for posterity.
 //!
 //! Both those operations extend straightforwardly to a list or pattern-stacks, i.e. a matrix, by
 //! working row-by-row. Popping a constructor ends up keeping only the matrix rows that start with
@@ -120,73 +134,88 @@
 //! operates principally on the first component of the matrix and new pattern-stack `p`.
 //! This algorithm is realised in the `is_useful` function.
 //!
-//! Base case. (`n = 0`, i.e., an empty tuple pattern)
-//!     - If `P` already contains an empty pattern (i.e., if the number of patterns `m > 0`),
-//!       then `U(P, p)` is false.
-//!     - Otherwise, `P` must be empty, so `U(P, p)` is true.
+//! Base case (`n = 0`, i.e., an empty tuple pattern):
+//! - If `P` already contains an empty pattern (i.e., if the number of patterns `m > 0`), then
+//!   `U(P, p)` is false.
+//! - Otherwise, `P` must be empty, so `U(P, p)` is true.
+//!
+//! Inductive step (`n > 0`, i.e., whether there's at least one column [which may then be expanded
+//! into further columns later]). We're going to match on the top of the new pattern-stack, `p_1`:
+//!
+//! - If `p_1 == c(r_1, .., r_a)`, i.e. we have a constructor pattern.
+//!   Then, the usefulness of `p_1` can be reduced to whether it is useful when
+//!   we ignore all the patterns in the first column of `P` that involve other constructors.
+//!   This is where `S(c, P)` comes in:
+//!
+//!   ```text
+//!   U(P, p) := U(S(c, P), S(c, p))
+//!   ```
 //!
-//! Inductive step. (`n > 0`, i.e., whether there's at least one column
-//!                  [which may then be expanded into further columns later])
-//!     We're going to match on the top of the new pattern-stack, `p_1`.
-//!         - If `p_1 == c(r_1, .., r_a)`, i.e. we have a constructor pattern.
-//!           Then, the usefulness of `p_1` can be reduced to whether it is useful when
-//!           we ignore all the patterns in the first column of `P` that involve other constructors.
-//!           This is where `S(c, P)` comes in:
-//!           `U(P, p) := U(S(c, P), S(c, p))`
-//!           This special case is handled in `is_useful_specialized`.
+//!   This special case is handled in `is_useful_specialized`.
 //!
-//!           For example, if `P` is:
-//!           [
-//!               [Some(true), _],
-//!               [None, 0],
-//!           ]
-//!           and `p` is [Some(false), 0], then we don't care about row 2 since we know `p` only
-//!           matches values that row 2 doesn't. For row 1 however, we need to dig into the
-//!           arguments of `Some` to know whether some new value is covered. So we compute
-//!           `U([[true, _]], [false, 0])`.
+//!   For example, if `P` is:
 //!
-//!         - If `p_1 == _`, then we look at the list of constructors that appear in the first
-//!               component of the rows of `P`:
-//!             + If there are some constructors that aren't present, then we might think that the
-//!               wildcard `_` is useful, since it covers those constructors that weren't covered
-//!               before.
-//!               That's almost correct, but only works if there were no wildcards in those first
-//!               components. So we need to check that `p` is useful with respect to the rows that
-//!               start with a wildcard, if there are any. This is where `D` comes in:
-//!               `U(P, p) := U(D(P), D(p))`
+//!   ```text
+//!   [
+//!       [Some(true), _],
+//!       [None, 0],
+//!   ]
+//!   ```
 //!
-//!               For example, if `P` is:
-//!               [
-//!                   [_, true, _],
-//!                   [None, false, 1],
-//!               ]
-//!               and `p` is [_, false, _], the `Some` constructor doesn't appear in `P`. So if we
-//!               only had row 2, we'd know that `p` is useful. However row 1 starts with a
-//!               wildcard, so we need to check whether `U([[true, _]], [false, 1])`.
+//!   and `p` is `[Some(false), 0]`, then we don't care about row 2 since we know `p` only
+//!   matches values that row 2 doesn't. For row 1 however, we need to dig into the
+//!   arguments of `Some` to know whether some new value is covered. So we compute
+//!   `U([[true, _]], [false, 0])`.
 //!
-//!             + Otherwise, all possible constructors (for the relevant type) are present. In this
-//!               case we must check whether the wildcard pattern covers any unmatched value. For
-//!               that, we can think of the `_` pattern as a big OR-pattern that covers all
-//!               possible constructors. For `Option`, that would mean `_ = None | Some(_)` for
-//!               example. The wildcard pattern is useful in this case if it is useful when
-//!               specialized to one of the possible constructors. So we compute:
-//!               `U(P, p) := ∃(k ϵ constructors) U(S(k, P), S(k, p))`
+//! - If `p_1 == _`, then we look at the list of constructors that appear in the first component of
+//!   the rows of `P`:
+//!     - If there are some constructors that aren't present, then we might think that the
+//!       wildcard `_` is useful, since it covers those constructors that weren't covered
+//!       before.
+//!       That's almost correct, but only works if there were no wildcards in those first
+//!       components. So we need to check that `p` is useful with respect to the rows that
+//!       start with a wildcard, if there are any. This is where `D` comes in:
+//!       `U(P, p) := U(D(P), D(p))`
 //!
-//!               For example, if `P` is:
-//!               [
-//!                   [Some(true), _],
-//!                   [None, false],
-//!               ]
-//!               and `p` is [_, false], both `None` and `Some` constructors appear in the first
-//!               components of `P`. We will therefore try popping both constructors in turn: we
-//!               compute U([[true, _]], [_, false]) for the `Some` constructor, and U([[false]],
-//!               [false]) for the `None` constructor. The first case returns true, so we know that
-//!               `p` is useful for `P`. Indeed, it matches `[Some(false), _]` that wasn't matched
-//!               before.
+//!       For example, if `P` is:
+//!       ```text
+//!       [
+//!           [_, true, _],
+//!           [None, false, 1],
+//!       ]
+//!       ```
+//!       and `p` is `[_, false, _]`, the `Some` constructor doesn't appear in `P`. So if we
+//!       only had row 2, we'd know that `p` is useful. However row 1 starts with a
+//!       wildcard, so we need to check whether `U([[true, _]], [false, 1])`.
 //!
-//!         - If `p_1 == r_1 | r_2`, then the usefulness depends on each `r_i` separately:
-//!           `U(P, p) := U(P, (r_1, p_2, .., p_n))
-//!                    || U(P, (r_2, p_2, .., p_n))`
+//!     - Otherwise, all possible constructors (for the relevant type) are present. In this
+//!       case we must check whether the wildcard pattern covers any unmatched value. For
+//!       that, we can think of the `_` pattern as a big OR-pattern that covers all
+//!       possible constructors. For `Option`, that would mean `_ = None | Some(_)` for
+//!       example. The wildcard pattern is useful in this case if it is useful when
+//!       specialized to one of the possible constructors. So we compute:
+//!       `U(P, p) := ∃(k ϵ constructors) U(S(k, P), S(k, p))`
+//!
+//!       For example, if `P` is:
+//!       ```text
+//!       [
+//!           [Some(true), _],
+//!           [None, false],
+//!       ]
+//!       ```
+//!       and `p` is `[_, false]`, both `None` and `Some` constructors appear in the first
+//!       components of `P`. We will therefore try popping both constructors in turn: we
+//!       compute `U([[true, _]], [_, false])` for the `Some` constructor, and `U([[false]],
+//!       [false])` for the `None` constructor. The first case returns true, so we know that
+//!       `p` is useful for `P`. Indeed, it matches `[Some(false), _]` that wasn't matched
+//!       before.
+//!
+//! - If `p_1 == r_1 | r_2`, then the usefulness depends on each `r_i` separately:
+//!
+//!   ```text
+//!   U(P, p) := U(P, (r_1, p_2, .., p_n))
+//!            || U(P, (r_2, p_2, .., p_n))
+//!   ```
 use std::sync::Arc;
 
 use smallvec::{smallvec, SmallVec};
@@ -283,20 +312,16 @@ impl PatStack {
         Self(v)
     }
 
-    fn is_empty(&self) -> bool {
-        self.0.is_empty()
-    }
-
-    fn head(&self) -> PatIdOrWild {
-        self.0[0]
-    }
-
     fn get_head(&self) -> Option<PatIdOrWild> {
         self.0.first().copied()
     }
 
+    fn tail(&self) -> &[PatIdOrWild] {
+        self.0.get(1..).unwrap_or(&[])
+    }
+
     fn to_tail(&self) -> PatStack {
-        Self::from_slice(&self.0[1..])
+        Self::from_slice(self.tail())
     }
 
     fn replace_head_with<I, T>(&self, pats: I) -> PatStack
@@ -318,7 +343,7 @@ impl PatStack {
     ///
     /// See the module docs and the associated documentation in rustc for details.
     fn specialize_wildcard(&self, cx: &MatchCheckCtx) -> Option<PatStack> {
-        if matches!(self.head().as_pat(cx), Pat::Wild) {
+        if matches!(self.get_head()?.as_pat(cx), Pat::Wild) {
             Some(self.to_tail())
         } else {
             None
@@ -333,7 +358,13 @@ impl PatStack {
         cx: &MatchCheckCtx,
         constructor: &Constructor,
     ) -> MatchCheckResult<Option<PatStack>> {
-        let result = match (self.head().as_pat(cx), constructor) {
+        let head = match self.get_head() {
+            Some(head) => head,
+            None => return Ok(None),
+        };
+
+        let head_pat = head.as_pat(cx);
+        let result = match (head_pat, constructor) {
             (Pat::Tuple { args: ref pat_ids, ellipsis }, Constructor::Tuple { arity: _ }) => {
                 if ellipsis.is_some() {
                     // If there are ellipsis here, we should add the correct number of
@@ -360,7 +391,7 @@ impl PatStack {
             (Pat::Wild, constructor) => Some(self.expand_wildcard(cx, constructor)?),
             (Pat::Path(_), Constructor::Enum(constructor)) => {
                 // unit enum variants become `Pat::Path`
-                let pat_id = self.head().as_id().expect("we know this isn't a wild");
+                let pat_id = head.as_id().expect("we know this isn't a wild");
                 if !enum_variant_matches(cx, pat_id, *constructor) {
                     None
                 } else {
@@ -371,7 +402,7 @@ impl PatStack {
                 Pat::TupleStruct { args: ref pat_ids, ellipsis, .. },
                 Constructor::Enum(enum_constructor),
             ) => {
-                let pat_id = self.head().as_id().expect("we know this isn't a wild");
+                let pat_id = head.as_id().expect("we know this isn't a wild");
                 if !enum_variant_matches(cx, pat_id, *enum_constructor) {
                     None
                 } else {
@@ -411,7 +442,7 @@ impl PatStack {
                 }
             }
             (Pat::Record { args: ref arg_patterns, .. }, Constructor::Enum(e)) => {
-                let pat_id = self.head().as_id().expect("we know this isn't a wild");
+                let pat_id = head.as_id().expect("we know this isn't a wild");
                 if !enum_variant_matches(cx, pat_id, *e) {
                     None
                 } else {
@@ -457,7 +488,7 @@ impl PatStack {
     ) -> MatchCheckResult<PatStack> {
         assert_eq!(
             Pat::Wild,
-            self.head().as_pat(cx),
+            self.get_head().expect("expand_wildcard called on empty PatStack").as_pat(cx),
             "expand_wildcard must only be called on PatStack with wild at head",
         );
 
@@ -475,7 +506,6 @@ impl PatStack {
     }
 }
 
-#[derive(Debug)]
 /// A collection of PatStack.
 ///
 /// This type is modeled from the struct of the same name in `rustc`.
@@ -502,7 +532,7 @@ impl Matrix {
     }
 
     fn heads(&self) -> Vec<PatIdOrWild> {
-        self.0.iter().map(|p| p.head()).collect()
+        self.0.iter().flat_map(|p| p.get_head()).collect()
     }
 
     /// Computes `D(self)` for each contained PatStack.
@@ -589,13 +619,16 @@ pub(crate) fn is_useful(
         _ => (),
     }
 
-    if v.is_empty() {
-        let result = if matrix.is_empty() { Usefulness::Useful } else { Usefulness::NotUseful };
+    let head = match v.get_head() {
+        Some(head) => head,
+        None => {
+            let result = if matrix.is_empty() { Usefulness::Useful } else { Usefulness::NotUseful };
 
-        return Ok(result);
-    }
+            return Ok(result);
+        }
+    };
 
-    if let Pat::Or(pat_ids) = v.head().as_pat(cx) {
+    if let Pat::Or(pat_ids) = head.as_pat(cx) {
         let mut found_unimplemented = false;
         let any_useful = pat_ids.iter().any(|&pat_id| {
             let v = PatStack::from_pattern(pat_id);
@@ -619,7 +652,7 @@ pub(crate) fn is_useful(
         };
     }
 
-    if let Some(constructor) = pat_constructor(cx, v.head())? {
+    if let Some(constructor) = pat_constructor(cx, head)? {
         let matrix = matrix.specialize_constructor(&cx, &constructor)?;
         let v = v
             .specialize_constructor(&cx, &constructor)?
@@ -808,194 +841,193 @@ mod tests {
 
     pub(super) use crate::{diagnostics::MissingMatchArms, test_db::TestDB};
 
-    pub(super) fn check_diagnostic_message(content: &str) -> String {
-        TestDB::with_single_file(content).0.diagnostic::<MissingMatchArms>().0
+    pub(super) fn check_diagnostic_message(ra_fixture: &str) -> String {
+        TestDB::with_single_file(ra_fixture).0.diagnostic::<MissingMatchArms>().0
     }
 
-    pub(super) fn check_diagnostic(content: &str) {
+    pub(super) fn check_diagnostic(ra_fixture: &str) {
         let diagnostic_count =
-            TestDB::with_single_file(content).0.diagnostic::<MissingMatchArms>().1;
+            TestDB::with_single_file(ra_fixture).0.diagnostic::<MissingMatchArms>().1;
 
         assert_eq!(1, diagnostic_count, "no diagnostic reported");
     }
 
-    pub(super) fn check_no_diagnostic(content: &str) {
-        let diagnostic_count =
-            TestDB::with_single_file(content).0.diagnostic::<MissingMatchArms>().1;
+    pub(super) fn check_no_diagnostic(ra_fixture: &str) {
+        let (s, diagnostic_count) =
+            TestDB::with_single_file(ra_fixture).0.diagnostic::<MissingMatchArms>();
 
-        assert_eq!(0, diagnostic_count, "expected no diagnostic, found one");
+        assert_eq!(0, diagnostic_count, "expected no diagnostic, found one: {}", s);
     }
 
     #[test]
     fn empty_tuple_no_arms_diagnostic_message() {
-        let content = r"
-            fn test_fn() {
-                match () {
-                }
-            }
-        ";
-
         assert_snapshot!(
-            check_diagnostic_message(content),
+            check_diagnostic_message(r"
+                fn test_fn() {
+                    match () {
+                    }
+                }
+            "),
             @"\"()\": Missing match arm\n"
         );
     }
 
     #[test]
     fn empty_tuple_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match () {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn empty_tuple_wild() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match () {
                     _ => {}
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn empty_tuple_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match () {
                     () => {}
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_empty_tuple_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match (()) {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_empty_tuple_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (()) {
                     (()) => {}
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_two_empty_tuple_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match ((), ()) {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_two_empty_tuple_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match ((), ()) {
                     ((), ()) => {}
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn bool_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match false {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn bool_missing_arm() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match false {
                     true => {}
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn bool_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match false {
                     true => {}
                     false => {}
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true) {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true) {
                     (true, true) => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_missing_arm() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true) {
                     (false, true) => {},
@@ -1003,14 +1035,14 @@ mod tests {
                     (true, false) => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_with_wilds() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true) {
                     (false, _) => {},
@@ -1018,14 +1050,14 @@ mod tests {
                     (_, true) => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true) {
                     (true, true) => {},
@@ -1034,27 +1066,27 @@ mod tests {
                     (false, false) => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_binding_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true) {
                     (true, _x) => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_binding_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true) {
                     (true, _x) => {},
@@ -1062,80 +1094,80 @@ mod tests {
                     (false, false) => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_with_ellipsis_at_end_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true, false) {
                     (false, ..) => {},
                     (true, ..) => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_with_ellipsis_at_beginning_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true, false) {
                     (.., false) => {},
                     (.., true) => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_with_ellipsis_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true, false) {
                     (..) => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_tuple_and_bools_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match (false, ((), false)) {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_tuple_and_bools_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match (false, ((), false)) {
                     (true, ((), true)) => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_tuple_and_bools_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, ((), false)) {
                     (true, ((), true)) => {},
@@ -1144,27 +1176,27 @@ mod tests {
                     (false, ((), false)) => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_tuple_and_bools_wildcard_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             fn test_fn() {
                 match (false, ((), false)) {
                     (true, _) => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_tuple_and_bools_wildcard_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, ((), false)) {
                     (true, ((), true)) => {},
@@ -1172,14 +1204,14 @@ mod tests {
                     (false, _) => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1188,14 +1220,14 @@ mod tests {
                 match Either::A {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1205,14 +1237,14 @@ mod tests {
                     Either::A => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1223,14 +1255,14 @@ mod tests {
                     Either::B => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_ref_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1240,14 +1272,14 @@ mod tests {
                     Either::A => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_ref_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1258,14 +1290,14 @@ mod tests {
                     Either::B => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_containing_bool_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B,
@@ -1274,14 +1306,14 @@ mod tests {
                 match Either::B {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_containing_bool_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B,
@@ -1292,14 +1324,14 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_containing_bool_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B,
@@ -1311,14 +1343,14 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_containing_bool_with_wild_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B,
@@ -1329,14 +1361,14 @@ mod tests {
                     _ => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_containing_bool_with_wild_2_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B,
@@ -1347,14 +1379,14 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_different_sizes_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B(bool, bool),
@@ -1365,14 +1397,14 @@ mod tests {
                     Either::B(false, _) => (),
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_different_sizes_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B(bool, bool),
@@ -1384,14 +1416,14 @@ mod tests {
                     Either::B(false, _) => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn or_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B(bool, bool),
@@ -1403,14 +1435,14 @@ mod tests {
                     Either::B(false, _) => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_enum_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool),
                 B(bool, bool),
@@ -1427,14 +1459,16 @@ mod tests {
                     (Either::B(_, _), Either2::D) => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn mismatched_types() {
-        let content = r"
+        // Match statements with arms that don't match the
+        // expression pattern do not fire this diagnostic.
+        check_no_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1449,47 +1483,47 @@ mod tests {
                     Either2::D => (),
                 }
             }
-        ";
-
-        // Match statements with arms that don't match the
-        // expression pattern do not fire this diagnostic.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn mismatched_types_with_different_arity() {
-        let content = r"
+        // Match statements with arms that don't match the
+        // expression pattern do not fire this diagnostic.
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (true, false) {
                     (true, false, true) => (),
                     (true) => (),
                 }
             }
-        ";
-
-        // Match statements with arms that don't match the
-        // expression pattern do not fire this diagnostic.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn malformed_match_arm_tuple_missing_pattern() {
-        let content = r"
+        // Match statements with arms that don't match the
+        // expression pattern do not fire this diagnostic.
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (0) {
                     () => (),
                 }
             }
-        ";
-
-        // Match statements with arms that don't match the
-        // expression pattern do not fire this diagnostic.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn malformed_match_arm_tuple_enum_missing_pattern() {
-        let content = r"
+        // We are testing to be sure we don't panic here when the match
+        // arm `Either::B` is missing its pattern.
+        check_no_diagnostic(
+            r"
             enum Either {
                 A,
                 B(u32),
@@ -1500,32 +1534,30 @@ mod tests {
                     Either::B() => (),
                 }
             }
-        ";
-
-        // We are testing to be sure we don't panic here when the match
-        // arm `Either::B` is missing its pattern.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_not_in_scope() {
-        let content = r"
+        // The enum is not in scope so we don't perform exhaustiveness
+        // checking, but we want to be sure we don't panic here (and
+        // we don't create a diagnostic).
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match Foo::Bar {
                     Foo::Baz => (),
                 }
             }
-        ";
-
-        // The enum is not in scope so we don't perform exhaustiveness
-        // checking, but we want to be sure we don't panic here (and
-        // we don't create a diagnostic).
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn expr_diverges() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1536,14 +1568,14 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn expr_loop_with_break() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1554,14 +1586,14 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn expr_partially_diverges() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either<T> {
                 A(T),
                 B,
@@ -1575,14 +1607,14 @@ mod tests {
                     Either::B => 0,
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_no_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A { foo: bool },
                 B,
@@ -1592,14 +1624,14 @@ mod tests {
                 match a {
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_missing_arms() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A { foo: bool },
                 B,
@@ -1610,14 +1642,14 @@ mod tests {
                     Either::A { foo: true } => (),
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A { foo: bool },
                 B,
@@ -1630,14 +1662,17 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_missing_field_no_diagnostic() {
-        let content = r"
+        // When `Either::A` is missing a struct member, we don't want
+        // to fire the missing match arm diagnostic. This should fire
+        // some other diagnostic.
+        check_no_diagnostic(
+            r"
             enum Either {
                 A { foo: bool },
                 B,
@@ -1649,17 +1684,16 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        // When `Either::A` is missing a struct member, we don't want
-        // to fire the missing match arm diagnostic. This should fire
-        // some other diagnostic.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_missing_field_missing_match_arm() {
-        let content = r"
+        // Even though `Either::A` is missing fields, we still want to fire
+        // the missing arm diagnostic here, since we know `Either::B` is missing.
+        check_diagnostic(
+            r"
             enum Either {
                 A { foo: bool },
                 B,
@@ -1670,16 +1704,14 @@ mod tests {
                     Either::A { } => (),
                 }
             }
-        ";
-
-        // Even though `Either::A` is missing fields, we still want to fire
-        // the missing arm diagnostic here, since we know `Either::B` is missing.
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_no_diagnostic_wild() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A { foo: bool },
                 B,
@@ -1691,14 +1723,14 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_fields_out_of_order_missing_arm() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A { foo: bool, bar: () },
                 B,
@@ -1710,14 +1742,14 @@ mod tests {
                     Either::A { foo: true, bar: () } => (),
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_fields_out_of_order_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A { foo: bool, bar: () },
                 B,
@@ -1730,89 +1762,89 @@ mod tests {
                     Either::B => (),
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_record_ellipsis_missing_arm() {
-        let content = r"
-             enum Either {
-                 A { foo: bool, bar: bool },
-                 B,
-             }
-             fn test_fn() {
-                 match Either::B {
-                     Either::A { foo: true, .. } => (),
-                     Either::B => (),
-                 }
-             }
-         ";
-
-        check_diagnostic(content);
+        check_diagnostic(
+            r"
+            enum Either {
+                A { foo: bool, bar: bool },
+                B,
+            }
+            fn test_fn() {
+                match Either::B {
+                    Either::A { foo: true, .. } => (),
+                    Either::B => (),
+                }
+            }
+        ",
+        );
     }
 
     #[test]
     fn enum_record_ellipsis_no_diagnostic() {
-        let content = r"
-             enum Either {
-                 A { foo: bool, bar: bool },
-                 B,
-             }
-             fn test_fn() {
-                 let a = Either::A { foo: true };
-                 match a {
-                     Either::A { foo: true, .. } => (),
-                     Either::A { foo: false, .. } => (),
-                     Either::B => (),
-                 }
-             }
-         ";
-
-        check_no_diagnostic(content);
+        check_no_diagnostic(
+            r"
+            enum Either {
+                A { foo: bool, bar: bool },
+                B,
+            }
+            fn test_fn() {
+                let a = Either::A { foo: true };
+                match a {
+                    Either::A { foo: true, .. } => (),
+                    Either::A { foo: false, .. } => (),
+                    Either::B => (),
+                }
+            }
+        ",
+        );
     }
 
     #[test]
     fn enum_record_ellipsis_all_fields_missing_arm() {
-        let content = r"
-             enum Either {
-                 A { foo: bool, bar: bool },
-                 B,
-             }
-             fn test_fn() {
-                 let a = Either::B;
-                 match a {
-                     Either::A { .. } => (),
-                 }
-             }
-         ";
-
-        check_diagnostic(content);
+        check_diagnostic(
+            r"
+            enum Either {
+                A { foo: bool, bar: bool },
+                B,
+            }
+            fn test_fn() {
+                let a = Either::B;
+                match a {
+                    Either::A { .. } => (),
+                }
+            }
+        ",
+        );
     }
 
     #[test]
     fn enum_record_ellipsis_all_fields_no_diagnostic() {
-        let content = r"
-             enum Either {
-                 A { foo: bool, bar: bool },
-                 B,
-             }
-             fn test_fn() {
-                 let a = Either::B;
-                 match a {
-                     Either::A { .. } => (),
-                     Either::B => (),
-                 }
-             }
-         ";
-
-        check_no_diagnostic(content);
+        check_no_diagnostic(
+            r"
+            enum Either {
+                A { foo: bool, bar: bool },
+                B,
+            }
+            fn test_fn() {
+                let a = Either::B;
+                match a {
+                    Either::A { .. } => (),
+                    Either::B => (),
+                }
+            }
+        ",
+        );
     }
 
     #[test]
     fn enum_tuple_partial_ellipsis_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool, bool, bool, bool),
                 B,
@@ -1826,14 +1858,14 @@ mod tests {
                     Either::B => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_tuple_partial_ellipsis_2_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool, bool, bool, bool),
                 B,
@@ -1847,14 +1879,14 @@ mod tests {
                     Either::B => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_tuple_partial_ellipsis_missing_arm() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A(bool, bool, bool, bool),
                 B,
@@ -1867,14 +1899,14 @@ mod tests {
                     Either::B => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_tuple_partial_ellipsis_2_missing_arm() {
-        let content = r"
+        check_diagnostic(
+            r"
             enum Either {
                 A(bool, bool, bool, bool),
                 B,
@@ -1887,14 +1919,14 @@ mod tests {
                     Either::B => {},
                 }
             }
-        ";
-
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_tuple_ellipsis_no_diagnostic() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A(bool, bool, bool, bool),
                 B,
@@ -1905,51 +1937,51 @@ mod tests {
                     Either::B => {},
                 }
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_never() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Never {}
 
             fn test_fn(never: Never) {
                 match never {}
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn type_never() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             fn test_fn(never: !) {
                 match never {}
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn enum_never_ref() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Never {}
 
             fn test_fn(never: &Never) {
                 match never {}
             }
-        ";
-
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn expr_diverges_missing_arm() {
-        let content = r"
+        check_no_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -1959,9 +1991,49 @@ mod tests {
                     Either::A => (),
                 }
             }
-        ";
+        ",
+        );
+    }
+
+    #[test]
+    fn or_pattern_panic() {
+        check_no_diagnostic(
+            r"
+            pub enum Category {
+                Infinity,
+                Zero,
+            }
+
+            fn panic(a: Category, b: Category) {
+                match (a, b) {
+                    (Category::Zero | Category::Infinity, _) => {}
+                    (_, Category::Zero | Category::Infinity) => {}
+                }
+            }
+        ",
+        );
+    }
 
-        check_no_diagnostic(content);
+    #[test]
+    fn or_pattern_panic_2() {
+        // FIXME: This is a false positive, but the code used to cause a panic in the match checker,
+        // so this acts as a regression test for that.
+        check_diagnostic(
+            r"
+            pub enum Category {
+                Infinity,
+                Zero,
+            }
+
+            fn panic(a: Category, b: Category) {
+                match (a, b) {
+                    (Category::Infinity, Category::Infinity) | (Category::Zero, Category::Zero) => {}
+
+                    (Category::Infinity | Category::Zero, _) => {}
+                }
+            }
+        ",
+        );
     }
 }
 
@@ -1981,23 +2053,26 @@ mod false_negatives {
 
     #[test]
     fn integers() {
-        let content = r"
+        // This is a false negative.
+        // We don't currently check integer exhaustiveness.
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match 5 {
                     10 => (),
                     11..20 => (),
                 }
             }
-        ";
-
-        // This is a false negative.
-        // We don't currently check integer exhaustiveness.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn internal_or() {
-        let content = r"
+        // This is a false negative.
+        // We do not currently handle patterns with internal `or`s.
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 enum Either {
                     A(bool),
@@ -2007,16 +2082,18 @@ mod false_negatives {
                     Either::A(true | false) => (),
                 }
             }
-        ";
-
-        // This is a false negative.
-        // We do not currently handle patterns with internal `or`s.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn expr_loop_missing_arm() {
-        let content = r"
+        // This is a false negative.
+        // We currently infer the type of `loop { break Foo::A }` to `!`, which
+        // causes us to skip the diagnostic since `Either::A` doesn't type check
+        // with `!`.
+        check_diagnostic(
+            r"
             enum Either {
                 A,
                 B,
@@ -2026,48 +2103,46 @@ mod false_negatives {
                     Either::A => (),
                 }
             }
-        ";
-
-        // This is a false negative.
-        // We currently infer the type of `loop { break Foo::A }` to `!`, which
-        // causes us to skip the diagnostic since `Either::A` doesn't type check
-        // with `!`.
-        check_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_with_ellipsis_at_end_missing_arm() {
-        let content = r"
+        // This is a false negative.
+        // We don't currently handle tuple patterns with ellipsis.
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true, false) {
                     (false, ..) => {},
                 }
             }
-        ";
-
-        // This is a false negative.
-        // We don't currently handle tuple patterns with ellipsis.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn tuple_of_bools_with_ellipsis_at_beginning_missing_arm() {
-        let content = r"
+        // This is a false negative.
+        // We don't currently handle tuple patterns with ellipsis.
+        check_no_diagnostic(
+            r"
             fn test_fn() {
                 match (false, true, false) {
                     (.., false) => {},
                 }
             }
-        ";
-
-        // This is a false negative.
-        // We don't currently handle tuple patterns with ellipsis.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 
     #[test]
     fn struct_missing_arm() {
-        let content = r"
+        // This is a false negative.
+        // We don't currently handle structs.
+        check_no_diagnostic(
+            r"
             struct Foo {
                 a: bool,
             }
@@ -2076,10 +2151,7 @@ mod false_negatives {
                     Foo { a: true } => {},
                 }
             }
-        ";
-
-        // This is a false negative.
-        // We don't currently handle structs.
-        check_no_diagnostic(content);
+        ",
+        );
     }
 }
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index 2b9372b4b..f22232324 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -73,6 +73,7 @@ pub use lower::{
 pub use traits::{InEnvironment, Obligation, ProjectionPredicate, TraitEnvironment};
 
 pub use chalk_ir::{BoundVar, DebruijnIndex};
+use itertools::Itertools;
 
 /// A type constructor or type name: this might be something like the primitive
 /// type `bool`, a struct like `Vec`, or things like function pointers or
@@ -815,6 +816,11 @@ impl Ty {
         }
     }
 
+    /// If this is a `dyn Trait`, returns that trait.
+    pub fn dyn_trait(&self) -> Option<TraitId> {
+        self.dyn_trait_ref().map(|it| it.trait_)
+    }
+
     fn builtin_deref(&self) -> Option<Ty> {
         match self {
             Ty::Apply(a_ty) => match a_ty.ctor {
@@ -867,13 +873,56 @@ impl Ty {
         }
     }
 
-    /// If this is a `dyn Trait`, returns that trait.
-    pub fn dyn_trait(&self) -> Option<TraitId> {
+    pub fn impl_trait_bounds(&self, db: &dyn HirDatabase) -> Option<Vec<GenericPredicate>> {
         match self {
-            Ty::Dyn(predicates) => predicates.iter().find_map(|pred| match pred {
-                GenericPredicate::Implemented(tr) => Some(tr.trait_),
-                _ => None,
-            }),
+            Ty::Opaque(opaque_ty) => {
+                let predicates = match opaque_ty.opaque_ty_id {
+                    OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
+                        db.return_type_impl_traits(func).map(|it| {
+                            let data = (*it)
+                                .as_ref()
+                                .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
+                            data.clone().subst(&opaque_ty.parameters)
+                        })
+                    }
+                };
+
+                predicates.map(|it| it.value)
+            }
+            Ty::Placeholder(id) => {
+                let generic_params = db.generic_params(id.parent);
+                let param_data = &generic_params.types[id.local_id];
+                match param_data.provenance {
+                    hir_def::generics::TypeParamProvenance::ArgumentImplTrait => {
+                        let predicates = db
+                            .generic_predicates_for_param(*id)
+                            .into_iter()
+                            .map(|pred| pred.value.clone())
+                            .collect_vec();
+
+                        Some(predicates)
+                    }
+                    _ => None,
+                }
+            }
+            _ => None,
+        }
+    }
+
+    pub fn associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<TraitId> {
+        match self {
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::AssociatedType(type_alias_id), .. }) => {
+                match type_alias_id.lookup(db.upcast()).container {
+                    AssocContainerId::TraitId(trait_id) => Some(trait_id),
+                    _ => None,
+                }
+            }
+            Ty::Projection(projection_ty) => {
+                match projection_ty.associated_ty.lookup(db.upcast()).container {
+                    AssocContainerId::TraitId(trait_id) => Some(trait_id),
+                    _ => None,
+                }
+            }
             _ => None,
         }
     }
@@ -1057,5 +1106,5 @@ pub struct ReturnTypeImplTraits {
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub(crate) struct ReturnTypeImplTrait {
-    pub(crate) bounds: Binders<Vec<GenericPredicate>>,
+    pub bounds: Binders<Vec<GenericPredicate>>,
 }
diff --git a/crates/ra_ide/src/completion.rs b/crates/ra_ide/src/completion.rs
index a721e23c6..e1fcf379d 100644
--- a/crates/ra_ide/src/completion.rs
+++ b/crates/ra_ide/src/completion.rs
@@ -15,6 +15,7 @@ mod complete_unqualified_path;
 mod complete_postfix;
 mod complete_macro_in_item_position;
 mod complete_trait_impl;
+mod patterns;
 #[cfg(test)]
 mod test_utils;
 
diff --git a/crates/ra_ide/src/completion/complete_keyword.rs b/crates/ra_ide/src/completion/complete_keyword.rs
index fd95bc410..b2f621a11 100644
--- a/crates/ra_ide/src/completion/complete_keyword.rs
+++ b/crates/ra_ide/src/completion/complete_keyword.rs
@@ -1,11 +1,6 @@
 //! FIXME: write short doc here
 
-use ra_syntax::{
-    ast::{self, LoopBodyOwner},
-    match_ast, AstNode,
-    SyntaxKind::*,
-    SyntaxToken,
-};
+use ra_syntax::ast;
 
 use crate::completion::{
     CompletionContext, CompletionItem, CompletionItemKind, CompletionKind, Completions,
@@ -41,68 +36,122 @@ pub(super) fn complete_use_tree_keyword(acc: &mut Completions, ctx: &CompletionC
     }
 }
 
-fn keyword(ctx: &CompletionContext, kw: &str, snippet: &str) -> CompletionItem {
-    let res = CompletionItem::new(CompletionKind::Keyword, ctx.source_range(), kw)
-        .kind(CompletionItemKind::Keyword);
-
-    match ctx.config.snippet_cap {
-        Some(cap) => res.insert_snippet(cap, snippet),
-        _ => res.insert_text(if snippet.contains('$') { kw } else { snippet }),
+pub(super) fn complete_expr_keyword(acc: &mut Completions, ctx: &CompletionContext) {
+    let has_trait_or_impl_parent = ctx.has_impl_parent || ctx.has_trait_parent;
+    if ctx.trait_as_prev_sibling || ctx.impl_as_prev_sibling {
+        add_keyword(ctx, acc, "where", "where ");
+        return;
     }
-    .build()
-}
+    if ctx.unsafe_is_prev {
+        if ctx.has_item_list_or_source_file_parent || ctx.block_expr_parent {
+            add_keyword(ctx, acc, "fn", "fn $0() {}")
+        }
+
+        if (ctx.has_item_list_or_source_file_parent && !has_trait_or_impl_parent)
+            || ctx.block_expr_parent
+        {
+            add_keyword(ctx, acc, "trait", "trait $0 {}");
+            add_keyword(ctx, acc, "impl", "impl $0 {}");
+        }
 
-pub(super) fn complete_expr_keyword(acc: &mut Completions, ctx: &CompletionContext) {
-    if !ctx.is_trivial_path {
         return;
     }
+    if ctx.has_item_list_or_source_file_parent || ctx.block_expr_parent {
+        add_keyword(ctx, acc, "fn", "fn $0() {}");
+    }
+    if (ctx.has_item_list_or_source_file_parent && !has_trait_or_impl_parent)
+        || ctx.block_expr_parent
+    {
+        add_keyword(ctx, acc, "use", "use ");
+        add_keyword(ctx, acc, "impl", "impl $0 {}");
+        add_keyword(ctx, acc, "trait", "trait $0 {}");
+    }
 
-    let fn_def = match &ctx.function_syntax {
-        Some(it) => it,
-        None => return,
-    };
-    acc.add(keyword(ctx, "if", "if $0 {}"));
-    acc.add(keyword(ctx, "match", "match $0 {}"));
-    acc.add(keyword(ctx, "while", "while $0 {}"));
-    acc.add(keyword(ctx, "loop", "loop {$0}"));
+    if ctx.has_item_list_or_source_file_parent && !has_trait_or_impl_parent {
+        add_keyword(ctx, acc, "enum", "enum $0 {}");
+        add_keyword(ctx, acc, "struct", "struct $0 {}");
+        add_keyword(ctx, acc, "union", "union $0 {}");
+    }
 
+    if ctx.block_expr_parent || ctx.is_match_arm {
+        add_keyword(ctx, acc, "match", "match $0 {}");
+        add_keyword(ctx, acc, "loop", "loop {$0}");
+    }
+    if ctx.block_expr_parent {
+        add_keyword(ctx, acc, "while", "while $0 {}");
+    }
+    if ctx.if_is_prev || ctx.block_expr_parent {
+        add_keyword(ctx, acc, "let", "let ");
+    }
+    if ctx.if_is_prev || ctx.block_expr_parent || ctx.is_match_arm {
+        add_keyword(ctx, acc, "if", "if ");
+        add_keyword(ctx, acc, "if let", "if let ");
+    }
     if ctx.after_if {
-        acc.add(keyword(ctx, "else", "else {$0}"));
-        acc.add(keyword(ctx, "else if", "else if $0 {}"));
+        add_keyword(ctx, acc, "else", "else {$0}");
+        add_keyword(ctx, acc, "else if", "else if $0 {}");
+    }
+    if (ctx.has_item_list_or_source_file_parent && !has_trait_or_impl_parent)
+        || ctx.block_expr_parent
+    {
+        add_keyword(ctx, acc, "mod", "mod $0 {}");
+    }
+    if ctx.bind_pat_parent || ctx.ref_pat_parent {
+        add_keyword(ctx, acc, "mut", "mut ");
     }
-    if is_in_loop_body(&ctx.token) {
+    if ctx.has_item_list_or_source_file_parent || ctx.block_expr_parent {
+        add_keyword(ctx, acc, "const", "const ");
+        add_keyword(ctx, acc, "type", "type ");
+    }
+    if (ctx.has_item_list_or_source_file_parent && !has_trait_or_impl_parent)
+        || ctx.block_expr_parent
+    {
+        add_keyword(ctx, acc, "static", "static ");
+    };
+    if (ctx.has_item_list_or_source_file_parent && !has_trait_or_impl_parent)
+        || ctx.block_expr_parent
+    {
+        add_keyword(ctx, acc, "extern", "extern ");
+    }
+    if ctx.has_item_list_or_source_file_parent || ctx.block_expr_parent || ctx.is_match_arm {
+        add_keyword(ctx, acc, "unsafe", "unsafe ");
+    }
+    if ctx.in_loop_body {
         if ctx.can_be_stmt {
-            acc.add(keyword(ctx, "continue", "continue;"));
-            acc.add(keyword(ctx, "break", "break;"));
+            add_keyword(ctx, acc, "continue", "continue;");
+            add_keyword(ctx, acc, "break", "break;");
         } else {
-            acc.add(keyword(ctx, "continue", "continue"));
-            acc.add(keyword(ctx, "break", "break"));
+            add_keyword(ctx, acc, "continue", "continue");
+            add_keyword(ctx, acc, "break", "break");
         }
     }
+    if ctx.has_item_list_or_source_file_parent && !ctx.has_trait_parent {
+        add_keyword(ctx, acc, "pub", "pub ")
+    }
+
+    if !ctx.is_trivial_path {
+        return;
+    }
+    let fn_def = match &ctx.function_syntax {
+        Some(it) => it,
+        None => return,
+    };
     acc.add_all(complete_return(ctx, &fn_def, ctx.can_be_stmt));
 }
 
-fn is_in_loop_body(leaf: &SyntaxToken) -> bool {
-    // FIXME move this to CompletionContext and make it handle macros
-    for node in leaf.parent().ancestors() {
-        if node.kind() == FN_DEF || node.kind() == LAMBDA_EXPR {
-            break;
-        }
-        let loop_body = match_ast! {
-            match node {
-                ast::ForExpr(it) => it.loop_body(),
-                ast::WhileExpr(it) => it.loop_body(),
-                ast::LoopExpr(it) => it.loop_body(),
-                _ => None,
-            }
-        };
-        if let Some(body) = loop_body {
-            if body.syntax().text_range().contains_range(leaf.text_range()) {
-                return true;
-            }
-        }
+fn keyword(ctx: &CompletionContext, kw: &str, snippet: &str) -> CompletionItem {
+    let res = CompletionItem::new(CompletionKind::Keyword, ctx.source_range(), kw)
+        .kind(CompletionItemKind::Keyword);
+
+    match ctx.config.snippet_cap {
+        Some(cap) => res.insert_snippet(cap, snippet),
+        _ => res.insert_text(if snippet.contains('$') { kw } else { snippet }),
     }
-    false
+    .build()
+}
+
+fn add_keyword(ctx: &CompletionContext, acc: &mut Completions, kw: &str, snippet: &str) {
+    acc.add(keyword(ctx, kw, snippet));
 }
 
 fn complete_return(
@@ -121,327 +170,156 @@ fn complete_return(
 
 #[cfg(test)]
 mod tests {
-    use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
-    use insta::assert_debug_snapshot;
+    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use insta::assert_snapshot;
 
-    fn do_keyword_completion(code: &str) -> Vec<CompletionItem> {
-        do_completion(code, CompletionKind::Keyword)
+    fn get_keyword_completions(code: &str) -> String {
+        completion_list(code, CompletionKind::Keyword)
     }
 
     #[test]
-    fn completes_keywords_in_use_stmt() {
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                use <|>
-                ",
-            ),
+    fn test_keywords_in_use_stmt() {
+        assert_snapshot!(
+            get_keyword_completions(r"use <|>"),
             @r###"
-        [
-            CompletionItem {
-                label: "crate",
-                source_range: 21..21,
-                delete: 21..21,
-                insert: "crate::",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "self",
-                source_range: 21..21,
-                delete: 21..21,
-                insert: "self",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "super",
-                source_range: 21..21,
-                delete: 21..21,
-                insert: "super::",
-                kind: Keyword,
-            },
-        ]
+            kw crate
+            kw self
+            kw super
         "###
         );
 
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                use a::<|>
-                ",
-            ),
+        assert_snapshot!(
+            get_keyword_completions(r"use a::<|>"),
             @r###"
-        [
-            CompletionItem {
-                label: "self",
-                source_range: 24..24,
-                delete: 24..24,
-                insert: "self",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "super",
-                source_range: 24..24,
-                delete: 24..24,
-                insert: "super::",
-                kind: Keyword,
-            },
-        ]
+            kw self
+            kw super
         "###
         );
 
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                use a::{b, <|>}
-                ",
-            ),
+        assert_snapshot!(
+            get_keyword_completions(r"use a::{b, <|>}"),
             @r###"
-        [
-            CompletionItem {
-                label: "self",
-                source_range: 28..28,
-                delete: 28..28,
-                insert: "self",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "super",
-                source_range: 28..28,
-                delete: 28..28,
-                insert: "super::",
-                kind: Keyword,
-            },
-        ]
+            kw self
+            kw super
         "###
         );
     }
 
     #[test]
-    fn completes_various_keywords_in_function() {
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                fn quux() {
-                    <|>
-                }
-                ",
-            ),
+    fn test_keywords_at_source_file_level() {
+        assert_snapshot!(
+            get_keyword_completions(r"m<|>"),
             @r###"
-        [
-            CompletionItem {
-                label: "if",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "return;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw const
+            kw enum
+            kw extern
+            kw fn
+            kw impl
+            kw mod
+            kw pub
+            kw static
+            kw struct
+            kw trait
+            kw type
+            kw union
+            kw unsafe
+            kw use
         "###
         );
     }
 
     #[test]
-    fn completes_else_after_if() {
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                fn quux() {
-                    if true {
-                        ()
-                    } <|>
-                }
-                ",
-            ),
+    fn test_keywords_in_function() {
+        assert_snapshot!(
+            get_keyword_completions(r"fn quux() { <|> }"),
             @r###"
-        [
-            CompletionItem {
-                label: "else",
-                source_range: 108..108,
-                delete: 108..108,
-                insert: "else {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "else if",
-                source_range: 108..108,
-                delete: 108..108,
-                insert: "else if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "if",
-                source_range: 108..108,
-                delete: 108..108,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 108..108,
-                delete: 108..108,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 108..108,
-                delete: 108..108,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 108..108,
-                delete: 108..108,
-                insert: "return;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 108..108,
-                delete: 108..108,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw const
+            kw extern
+            kw fn
+            kw if
+            kw if let
+            kw impl
+            kw let
+            kw loop
+            kw match
+            kw mod
+            kw return
+            kw static
+            kw trait
+            kw type
+            kw unsafe
+            kw use
+            kw while
         "###
         );
     }
 
     #[test]
-    fn test_completion_return_value() {
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                fn quux() -> i32 {
-                    <|>
-                    92
-                }
-                ",
-            ),
+    fn test_keywords_inside_block() {
+        assert_snapshot!(
+            get_keyword_completions(r"fn quux() { if true { <|> } }"),
             @r###"
-        [
-            CompletionItem {
-                label: "if",
-                source_range: 56..56,
-                delete: 56..56,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 56..56,
-                delete: 56..56,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 56..56,
-                delete: 56..56,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 56..56,
-                delete: 56..56,
-                insert: "return $0;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 56..56,
-                delete: 56..56,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw const
+            kw extern
+            kw fn
+            kw if
+            kw if let
+            kw impl
+            kw let
+            kw loop
+            kw match
+            kw mod
+            kw return
+            kw static
+            kw trait
+            kw type
+            kw unsafe
+            kw use
+            kw while
         "###
         );
-        assert_debug_snapshot!(
-            do_keyword_completion(
+    }
+
+    #[test]
+    fn test_keywords_after_if() {
+        assert_snapshot!(
+            get_keyword_completions(
                 r"
                 fn quux() {
-                    <|>
-                    92
+                    if true {
+                        ()
+                    } <|>
                 }
                 ",
             ),
             @r###"
-        [
-            CompletionItem {
-                label: "if",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "return;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 49..49,
-                delete: 49..49,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw const
+            kw else
+            kw else if
+            kw extern
+            kw fn
+            kw if
+            kw if let
+            kw impl
+            kw let
+            kw loop
+            kw match
+            kw mod
+            kw return
+            kw static
+            kw trait
+            kw type
+            kw unsafe
+            kw use
+            kw while
         "###
         );
     }
 
     #[test]
-    fn dont_add_semi_after_return_if_not_a_statement() {
-        assert_debug_snapshot!(
-            do_keyword_completion(
+    fn test_keywords_in_match_arm() {
+        assert_snapshot!(
+            get_keyword_completions(
                 r"
                 fn quux() -> i32 {
                     match () {
@@ -451,336 +329,130 @@ mod tests {
                 ",
             ),
             @r###"
-        [
-            CompletionItem {
-                label: "if",
-                source_range: 97..97,
-                delete: 97..97,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 97..97,
-                delete: 97..97,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 97..97,
-                delete: 97..97,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 97..97,
-                delete: 97..97,
-                insert: "return $0",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 97..97,
-                delete: 97..97,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw if
+            kw if let
+            kw loop
+            kw match
+            kw return
+            kw unsafe
         "###
         );
     }
 
     #[test]
-    fn last_return_in_block_has_semi() {
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                fn quux() -> i32 {
-                    if condition {
-                        <|>
-                    }
-                }
-                ",
-            ),
+    fn test_keywords_in_trait_def() {
+        assert_snapshot!(
+            get_keyword_completions(r"trait My { <|> }"),
             @r###"
-        [
-            CompletionItem {
-                label: "if",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "return $0;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw const
+            kw fn
+            kw type
+            kw unsafe
         "###
         );
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                fn quux() -> i32 {
-                    if condition {
-                        <|>
-                    }
-                    let x = 92;
-                    x
-                }
-                ",
-            ),
+    }
+
+    #[test]
+    fn test_keywords_in_impl_def() {
+        assert_snapshot!(
+            get_keyword_completions(r"impl My { <|> }"),
             @r###"
-        [
-            CompletionItem {
-                label: "if",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "return $0;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 95..95,
-                delete: 95..95,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw const
+            kw fn
+            kw pub
+            kw type
+            kw unsafe
         "###
         );
     }
 
     #[test]
-    fn completes_break_and_continue_in_loops() {
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                fn quux() -> i32 {
-                    loop { <|> }
-                }
-                ",
-            ),
+    fn test_keywords_in_loop() {
+        assert_snapshot!(
+            get_keyword_completions(r"fn my() { loop { <|> } }"),
             @r###"
-        [
-            CompletionItem {
-                label: "break",
-                source_range: 63..63,
-                delete: 63..63,
-                insert: "break;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "continue",
-                source_range: 63..63,
-                delete: 63..63,
-                insert: "continue;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "if",
-                source_range: 63..63,
-                delete: 63..63,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 63..63,
-                delete: 63..63,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 63..63,
-                delete: 63..63,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 63..63,
-                delete: 63..63,
-                insert: "return $0;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 63..63,
-                delete: 63..63,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw break
+            kw const
+            kw continue
+            kw extern
+            kw fn
+            kw if
+            kw if let
+            kw impl
+            kw let
+            kw loop
+            kw match
+            kw mod
+            kw return
+            kw static
+            kw trait
+            kw type
+            kw unsafe
+            kw use
+            kw while
         "###
         );
+    }
 
-        // No completion: lambda isolates control flow
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                fn quux() -> i32 {
-                    loop { || { <|> } }
-                }
-                ",
-            ),
+    #[test]
+    fn test_keywords_after_unsafe_in_item_list() {
+        assert_snapshot!(
+            get_keyword_completions(r"unsafe <|>"),
             @r###"
-        [
-            CompletionItem {
-                label: "if",
-                source_range: 68..68,
-                delete: 68..68,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 68..68,
-                delete: 68..68,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 68..68,
-                delete: 68..68,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 68..68,
-                delete: 68..68,
-                insert: "return $0;",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 68..68,
-                delete: 68..68,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw fn
+            kw impl
+            kw trait
         "###
         );
     }
 
     #[test]
-    fn no_semi_after_break_continue_in_expr() {
-        assert_debug_snapshot!(
-            do_keyword_completion(
-                r"
-                fn f() {
-                    loop {
-                        match () {
-                            () => br<|>
-                        }
-                    }
-                }
-                ",
-            ),
+    fn test_keywords_after_unsafe_in_block_expr() {
+        assert_snapshot!(
+            get_keyword_completions(r"fn my_fn() { unsafe <|> }"),
             @r###"
-        [
-            CompletionItem {
-                label: "break",
-                source_range: 122..124,
-                delete: 122..124,
-                insert: "break",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "continue",
-                source_range: 122..124,
-                delete: 122..124,
-                insert: "continue",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "if",
-                source_range: 122..124,
-                delete: 122..124,
-                insert: "if $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "loop",
-                source_range: 122..124,
-                delete: 122..124,
-                insert: "loop {$0}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "match",
-                source_range: 122..124,
-                delete: 122..124,
-                insert: "match $0 {}",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "return",
-                source_range: 122..124,
-                delete: 122..124,
-                insert: "return",
-                kind: Keyword,
-            },
-            CompletionItem {
-                label: "while",
-                source_range: 122..124,
-                delete: 122..124,
-                insert: "while $0 {}",
-                kind: Keyword,
-            },
-        ]
+            kw fn
+            kw impl
+            kw trait
         "###
-        )
+        );
+    }
+
+    #[test]
+    fn test_mut_in_ref_and_in_fn_parameters_list() {
+        assert_snapshot!(
+            get_keyword_completions(r"fn my_fn(&<|>) {}"),
+            @r###"
+            kw mut
+        "###
+        );
+        assert_snapshot!(
+            get_keyword_completions(r"fn my_fn(<|>) {}"),
+            @r###"
+            kw mut
+        "###
+        );
+        assert_snapshot!(
+            get_keyword_completions(r"fn my_fn() { let &<|> }"),
+            @r###"
+            kw mut
+        "###
+        );
+    }
+
+    #[test]
+    fn test_where_keyword() {
+        assert_snapshot!(
+            get_keyword_completions(r"trait A <|>"),
+            @r###"
+            kw where
+        "###
+        );
+        assert_snapshot!(
+            get_keyword_completions(r"impl A <|>"),
+            @r###"
+            kw where
+        "###
+        );
     }
 }
diff --git a/crates/ra_ide/src/completion/complete_postfix.rs b/crates/ra_ide/src/completion/complete_postfix.rs
index 59b58bf98..b878aeb0a 100644
--- a/crates/ra_ide/src/completion/complete_postfix.rs
+++ b/crates/ra_ide/src/completion/complete_postfix.rs
@@ -91,7 +91,7 @@ pub(super) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
             &dot_receiver,
             "if",
             "if expr {}",
-            &format!("if {} {{$0}}", receiver_text),
+            &format!("if {} {{\n    $0\n}}", receiver_text),
         )
         .add_to(acc);
         postfix_snippet(
@@ -100,7 +100,7 @@ pub(super) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
             &dot_receiver,
             "while",
             "while expr {}",
-            &format!("while {} {{\n$0\n}}", receiver_text),
+            &format!("while {} {{\n    $0\n}}", receiver_text),
         )
         .add_to(acc);
     }
@@ -283,7 +283,7 @@ mod tests {
                 label: "if",
                 source_range: 89..89,
                 delete: 85..89,
-                insert: "if bar {$0}",
+                insert: "if bar {\n    $0\n}",
                 detail: "if expr {}",
             },
             CompletionItem {
@@ -318,7 +318,7 @@ mod tests {
                 label: "while",
                 source_range: 89..89,
                 delete: 85..89,
-                insert: "while bar {\n$0\n}",
+                insert: "while bar {\n    $0\n}",
                 detail: "while expr {}",
             },
         ]
diff --git a/crates/ra_ide/src/completion/completion_context.rs b/crates/ra_ide/src/completion/completion_context.rs
index c4646b727..560fb19e6 100644
--- a/crates/ra_ide/src/completion/completion_context.rs
+++ b/crates/ra_ide/src/completion/completion_context.rs
@@ -5,12 +5,17 @@ use ra_db::SourceDatabase;
 use ra_ide_db::RootDatabase;
 use ra_syntax::{
     algo::{find_covering_element, find_node_at_offset},
-    ast, match_ast, AstNode,
+    ast, match_ast, AstNode, NodeOrToken,
     SyntaxKind::*,
     SyntaxNode, SyntaxToken, TextRange, TextSize,
 };
 use ra_text_edit::Indel;
 
+use super::patterns::{
+    has_bind_pat_parent, has_block_expr_parent, has_impl_as_prev_sibling, has_impl_parent,
+    has_item_list_or_source_file_parent, has_ref_parent, has_trait_as_prev_sibling,
+    has_trait_parent, if_is_prev, is_in_loop_body, is_match_arm, unsafe_is_prev,
+};
 use crate::{call_info::ActiveParameter, completion::CompletionConfig, FilePosition};
 use test_utils::mark;
 
@@ -60,6 +65,18 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) is_path_type: bool,
     pub(super) has_type_args: bool,
     pub(super) attribute_under_caret: Option<ast::Attr>,
+    pub(super) unsafe_is_prev: bool,
+    pub(super) if_is_prev: bool,
+    pub(super) block_expr_parent: bool,
+    pub(super) bind_pat_parent: bool,
+    pub(super) ref_pat_parent: bool,
+    pub(super) in_loop_body: bool,
+    pub(super) has_trait_parent: bool,
+    pub(super) has_impl_parent: bool,
+    pub(super) trait_as_prev_sibling: bool,
+    pub(super) impl_as_prev_sibling: bool,
+    pub(super) is_match_arm: bool,
+    pub(super) has_item_list_or_source_file_parent: bool,
 }
 
 impl<'a> CompletionContext<'a> {
@@ -118,6 +135,18 @@ impl<'a> CompletionContext<'a> {
             has_type_args: false,
             dot_receiver_is_ambiguous_float_literal: false,
             attribute_under_caret: None,
+            unsafe_is_prev: false,
+            in_loop_body: false,
+            ref_pat_parent: false,
+            bind_pat_parent: false,
+            block_expr_parent: false,
+            has_trait_parent: false,
+            has_impl_parent: false,
+            trait_as_prev_sibling: false,
+            impl_as_prev_sibling: false,
+            if_is_prev: false,
+            is_match_arm: false,
+            has_item_list_or_source_file_parent: false,
         };
 
         let mut original_file = original_file.syntax().clone();
@@ -159,7 +188,7 @@ impl<'a> CompletionContext<'a> {
                 break;
             }
         }
-
+        ctx.fill_keyword_patterns(&hypothetical_file, offset);
         ctx.fill(&original_file, hypothetical_file, offset);
         Some(ctx)
     }
@@ -188,6 +217,24 @@ impl<'a> CompletionContext<'a> {
         self.sema.scope_at_offset(&self.token.parent(), self.offset)
     }
 
+    fn fill_keyword_patterns(&mut self, file_with_fake_ident: &SyntaxNode, offset: TextSize) {
+        let fake_ident_token = file_with_fake_ident.token_at_offset(offset).right_biased().unwrap();
+        let syntax_element = NodeOrToken::Token(fake_ident_token.clone());
+        self.block_expr_parent = has_block_expr_parent(syntax_element.clone());
+        self.unsafe_is_prev = unsafe_is_prev(syntax_element.clone());
+        self.if_is_prev = if_is_prev(syntax_element.clone());
+        self.bind_pat_parent = has_bind_pat_parent(syntax_element.clone());
+        self.ref_pat_parent = has_ref_parent(syntax_element.clone());
+        self.in_loop_body = is_in_loop_body(syntax_element.clone());
+        self.has_trait_parent = has_trait_parent(syntax_element.clone());
+        self.has_impl_parent = has_impl_parent(syntax_element.clone());
+        self.impl_as_prev_sibling = has_impl_as_prev_sibling(syntax_element.clone());
+        self.trait_as_prev_sibling = has_trait_as_prev_sibling(syntax_element.clone());
+        self.is_match_arm = is_match_arm(syntax_element.clone());
+        self.has_item_list_or_source_file_parent =
+            has_item_list_or_source_file_parent(syntax_element.clone());
+    }
+
     fn fill(
         &mut self,
         original_file: &SyntaxNode,
@@ -334,6 +381,7 @@ impl<'a> CompletionContext<'a> {
             self.is_path_type = path.syntax().parent().and_then(ast::PathType::cast).is_some();
             self.has_type_args = segment.type_arg_list().is_some();
 
+            #[allow(deprecated)]
             if let Some(path) = hir::Path::from_ast(path.clone()) {
                 if let Some(path_prefix) = path.qualifier() {
                     self.path_prefix = Some(path_prefix);
diff --git a/crates/ra_ide/src/completion/completion_item.rs b/crates/ra_ide/src/completion/completion_item.rs
index cfb7c1e38..98348b349 100644
--- a/crates/ra_ide/src/completion/completion_item.rs
+++ b/crates/ra_ide/src/completion/completion_item.rs
@@ -125,6 +125,32 @@ pub enum CompletionItemKind {
     Attribute,
 }
 
+impl CompletionItemKind {
+    #[cfg(test)]
+    pub(crate) fn tag(&self) -> &'static str {
+        match self {
+            CompletionItemKind::Snippet => "sn",
+            CompletionItemKind::Keyword => "kw",
+            CompletionItemKind::Module => "md",
+            CompletionItemKind::Function => "fn",
+            CompletionItemKind::BuiltinType => "bt",
+            CompletionItemKind::Struct => "st",
+            CompletionItemKind::Enum => "en",
+            CompletionItemKind::EnumVariant => "ev",
+            CompletionItemKind::Binding => "bn",
+            CompletionItemKind::Field => "fd",
+            CompletionItemKind::Static => "sc",
+            CompletionItemKind::Const => "ct",
+            CompletionItemKind::Trait => "tt",
+            CompletionItemKind::TypeAlias => "ta",
+            CompletionItemKind::Method => "me",
+            CompletionItemKind::TypeParam => "tp",
+            CompletionItemKind::Macro => "ma",
+            CompletionItemKind::Attribute => "at",
+        }
+    }
+}
+
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 pub(crate) enum CompletionKind {
     /// Parser-based keyword completion.
diff --git a/crates/ra_ide/src/completion/patterns.rs b/crates/ra_ide/src/completion/patterns.rs
new file mode 100644
index 000000000..b2fe13280
--- /dev/null
+++ b/crates/ra_ide/src/completion/patterns.rs
@@ -0,0 +1,194 @@
+//! Patterns telling us certain facts about current syntax element, they are used in completion context
+
+use ra_syntax::{
+    algo::non_trivia_sibling,
+    ast::{self, LoopBodyOwner},
+    match_ast, AstNode, Direction, NodeOrToken, SyntaxElement,
+    SyntaxKind::*,
+    SyntaxNode, SyntaxToken,
+};
+
+#[cfg(test)]
+use crate::completion::test_utils::check_pattern_is_applicable;
+
+pub(crate) fn has_trait_parent(element: SyntaxElement) -> bool {
+    not_same_range_ancestor(element)
+        .filter(|it| it.kind() == ITEM_LIST)
+        .and_then(|it| it.parent())
+        .filter(|it| it.kind() == TRAIT_DEF)
+        .is_some()
+}
+#[test]
+fn test_has_trait_parent() {
+    check_pattern_is_applicable(r"trait A { f<|> }", has_trait_parent);
+}
+
+pub(crate) fn has_impl_parent(element: SyntaxElement) -> bool {
+    not_same_range_ancestor(element)
+        .filter(|it| it.kind() == ITEM_LIST)
+        .and_then(|it| it.parent())
+        .filter(|it| it.kind() == IMPL_DEF)
+        .is_some()
+}
+#[test]
+fn test_has_impl_parent() {
+    check_pattern_is_applicable(r"impl A { f<|> }", has_impl_parent);
+}
+
+pub(crate) fn has_block_expr_parent(element: SyntaxElement) -> bool {
+    not_same_range_ancestor(element).filter(|it| it.kind() == BLOCK_EXPR).is_some()
+}
+#[test]
+fn test_has_block_expr_parent() {
+    check_pattern_is_applicable(r"fn my_fn() { let a = 2; f<|> }", has_block_expr_parent);
+}
+
+pub(crate) fn has_bind_pat_parent(element: SyntaxElement) -> bool {
+    element.ancestors().find(|it| it.kind() == BIND_PAT).is_some()
+}
+#[test]
+fn test_has_bind_pat_parent() {
+    check_pattern_is_applicable(r"fn my_fn(m<|>) {}", has_bind_pat_parent);
+    check_pattern_is_applicable(r"fn my_fn() { let m<|> }", has_bind_pat_parent);
+}
+
+pub(crate) fn has_ref_parent(element: SyntaxElement) -> bool {
+    not_same_range_ancestor(element)
+        .filter(|it| it.kind() == REF_PAT || it.kind() == REF_EXPR)
+        .is_some()
+}
+#[test]
+fn test_has_ref_parent() {
+    check_pattern_is_applicable(r"fn my_fn(&m<|>) {}", has_ref_parent);
+    check_pattern_is_applicable(r"fn my() { let &m<|> }", has_ref_parent);
+}
+
+pub(crate) fn has_item_list_or_source_file_parent(element: SyntaxElement) -> bool {
+    let ancestor = not_same_range_ancestor(element);
+    if !ancestor.is_some() {
+        return true;
+    }
+    ancestor.filter(|it| it.kind() == SOURCE_FILE || it.kind() == ITEM_LIST).is_some()
+}
+#[test]
+fn test_has_item_list_or_source_file_parent() {
+    check_pattern_is_applicable(r"i<|>", has_item_list_or_source_file_parent);
+    check_pattern_is_applicable(r"impl { f<|> }", has_item_list_or_source_file_parent);
+}
+
+pub(crate) fn is_match_arm(element: SyntaxElement) -> bool {
+    not_same_range_ancestor(element.clone()).filter(|it| it.kind() == MATCH_ARM).is_some()
+        && previous_sibling_or_ancestor_sibling(element)
+            .and_then(|it| it.into_token())
+            .filter(|it| it.kind() == FAT_ARROW)
+            .is_some()
+}
+#[test]
+fn test_is_match_arm() {
+    check_pattern_is_applicable(r"fn my_fn() { match () { () => m<|> } }", is_match_arm);
+}
+
+pub(crate) fn unsafe_is_prev(element: SyntaxElement) -> bool {
+    element
+        .into_token()
+        .and_then(|it| previous_non_trivia_token(it))
+        .filter(|it| it.kind() == UNSAFE_KW)
+        .is_some()
+}
+#[test]
+fn test_unsafe_is_prev() {
+    check_pattern_is_applicable(r"unsafe i<|>", unsafe_is_prev);
+}
+
+pub(crate) fn if_is_prev(element: SyntaxElement) -> bool {
+    element
+        .into_token()
+        .and_then(|it| previous_non_trivia_token(it))
+        .filter(|it| it.kind() == IF_KW)
+        .is_some()
+}
+#[test]
+fn test_if_is_prev() {
+    check_pattern_is_applicable(r"if l<|>", if_is_prev);
+}
+
+pub(crate) fn has_trait_as_prev_sibling(element: SyntaxElement) -> bool {
+    previous_sibling_or_ancestor_sibling(element).filter(|it| it.kind() == TRAIT_DEF).is_some()
+}
+#[test]
+fn test_has_trait_as_prev_sibling() {
+    check_pattern_is_applicable(r"trait A w<|> {}", has_trait_as_prev_sibling);
+}
+
+pub(crate) fn has_impl_as_prev_sibling(element: SyntaxElement) -> bool {
+    previous_sibling_or_ancestor_sibling(element).filter(|it| it.kind() == IMPL_DEF).is_some()
+}
+#[test]
+fn test_has_impl_as_prev_sibling() {
+    check_pattern_is_applicable(r"impl A w<|> {}", has_impl_as_prev_sibling);
+}
+
+pub(crate) fn is_in_loop_body(element: SyntaxElement) -> bool {
+    let leaf = match element {
+        NodeOrToken::Node(node) => node,
+        NodeOrToken::Token(token) => token.parent(),
+    };
+    for node in leaf.ancestors() {
+        if node.kind() == FN_DEF || node.kind() == LAMBDA_EXPR {
+            break;
+        }
+        let loop_body = match_ast! {
+            match node {
+                ast::ForExpr(it) => it.loop_body(),
+                ast::WhileExpr(it) => it.loop_body(),
+                ast::LoopExpr(it) => it.loop_body(),
+                _ => None,
+            }
+        };
+        if let Some(body) = loop_body {
+            if body.syntax().text_range().contains_range(leaf.text_range()) {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+fn not_same_range_ancestor(element: SyntaxElement) -> Option<SyntaxNode> {
+    element
+        .ancestors()
+        .take_while(|it| it.text_range() == element.text_range())
+        .last()
+        .and_then(|it| it.parent())
+}
+
+fn previous_non_trivia_token(token: SyntaxToken) -> Option<SyntaxToken> {
+    let mut token = token.prev_token();
+    while let Some(inner) = token.clone() {
+        if !inner.kind().is_trivia() {
+            return Some(inner);
+        } else {
+            token = inner.prev_token();
+        }
+    }
+    None
+}
+
+fn previous_sibling_or_ancestor_sibling(element: SyntaxElement) -> Option<SyntaxElement> {
+    let token_sibling = non_trivia_sibling(element.clone(), Direction::Prev);
+    if let Some(sibling) = token_sibling {
+        Some(sibling)
+    } else {
+        // if not trying to find first ancestor which has such a sibling
+        let node = match element {
+            NodeOrToken::Node(node) => node,
+            NodeOrToken::Token(token) => token.parent(),
+        };
+        let range = node.text_range();
+        let top_node = node.ancestors().take_while(|it| it.text_range() == range).last()?;
+        let prev_sibling_node = top_node.ancestors().find(|it| {
+            non_trivia_sibling(NodeOrToken::Node(it.to_owned()), Direction::Prev).is_some()
+        })?;
+        non_trivia_sibling(NodeOrToken::Node(prev_sibling_node), Direction::Prev)
+    }
+}
diff --git a/crates/ra_ide/src/completion/test_utils.rs b/crates/ra_ide/src/completion/test_utils.rs
index bf22452a2..1e16a43ca 100644
--- a/crates/ra_ide/src/completion/test_utils.rs
+++ b/crates/ra_ide/src/completion/test_utils.rs
@@ -5,25 +5,63 @@ use crate::{
     mock_analysis::{analysis_and_position, single_file_with_position},
     CompletionItem,
 };
+use hir::Semantics;
+use ra_syntax::{AstNode, NodeOrToken, SyntaxElement};
 
 pub(crate) fn do_completion(code: &str, kind: CompletionKind) -> Vec<CompletionItem> {
     do_completion_with_options(code, kind, &CompletionConfig::default())
 }
 
+pub(crate) fn completion_list(code: &str, kind: CompletionKind) -> String {
+    completion_list_with_options(code, kind, &CompletionConfig::default())
+}
+
 pub(crate) fn do_completion_with_options(
     code: &str,
     kind: CompletionKind,
     options: &CompletionConfig,
 ) -> Vec<CompletionItem> {
+    let mut kind_completions: Vec<CompletionItem> = get_all_completion_items(code, options)
+        .into_iter()
+        .filter(|c| c.completion_kind == kind)
+        .collect();
+    kind_completions.sort_by(|l, r| l.label().cmp(r.label()));
+    kind_completions
+}
+
+fn get_all_completion_items(code: &str, options: &CompletionConfig) -> Vec<CompletionItem> {
     let (analysis, position) = if code.contains("//-") {
         analysis_and_position(code)
     } else {
         single_file_with_position(code)
     };
-    let completions = analysis.completions(options, position).unwrap().unwrap();
-    let completion_items: Vec<CompletionItem> = completions.into();
-    let mut kind_completions: Vec<CompletionItem> =
-        completion_items.into_iter().filter(|c| c.completion_kind == kind).collect();
+    analysis.completions(options, position).unwrap().unwrap().into()
+}
+
+pub(crate) fn completion_list_with_options(
+    code: &str,
+    kind: CompletionKind,
+    options: &CompletionConfig,
+) -> String {
+    let mut kind_completions: Vec<CompletionItem> = get_all_completion_items(code, options)
+        .into_iter()
+        .filter(|c| c.completion_kind == kind)
+        .collect();
     kind_completions.sort_by_key(|c| c.label().to_owned());
     kind_completions
+        .into_iter()
+        .map(|it| format!("{} {}\n", it.kind().unwrap().tag(), it.label()))
+        .collect()
+}
+
+pub(crate) fn check_pattern_is_applicable(code: &str, check: fn(SyntaxElement) -> bool) {
+    let (analysis, pos) = single_file_with_position(code);
+    analysis
+        .with_db(|db| {
+            let sema = Semantics::new(db);
+            let original_file = sema.parse(pos.file_id);
+            let token = original_file.syntax().token_at_offset(pos.offset).left_biased().unwrap();
+            assert!(check(NodeOrToken::Token(token)));
+        })
+        .unwrap();
 }
diff --git a/crates/ra_ide/src/diagnostics.rs b/crates/ra_ide/src/diagnostics.rs
index 365d52168..a88a978d7 100644
--- a/crates/ra_ide/src/diagnostics.rs
+++ b/crates/ra_ide/src/diagnostics.rs
@@ -11,7 +11,7 @@ use hir::{
     HasSource, HirDisplay, Semantics, VariantDef,
 };
 use itertools::Itertools;
-use ra_db::{RelativePath, SourceDatabase, SourceDatabaseExt};
+use ra_db::SourceDatabase;
 use ra_ide_db::RootDatabase;
 use ra_prof::profile;
 use ra_syntax::{
@@ -57,14 +57,10 @@ pub(crate) fn diagnostics(db: &RootDatabase, file_id: FileId) -> Vec<Diagnostic>
     })
     .on::<hir::diagnostics::UnresolvedModule, _>(|d| {
         let original_file = d.source().file_id.original_file(db);
-        let source_root = db.file_source_root(original_file);
-        let path = db
-            .file_relative_path(original_file)
-            .parent()
-            .unwrap_or_else(|| RelativePath::new(""))
-            .join(&d.candidate);
-        let fix =
-            Fix::new("Create module", FileSystemEdit::CreateFile { source_root, path }.into());
+        let fix = Fix::new(
+            "Create module",
+            FileSystemEdit::CreateFile { anchor: original_file, dst: d.candidate.clone() }.into(),
+        );
         res.borrow_mut().push(Diagnostic {
             range: sema.diagnostics_range(d).range,
             message: d.message(),
@@ -683,10 +679,10 @@ mod tests {
                             source_file_edits: [],
                             file_system_edits: [
                                 CreateFile {
-                                    source_root: SourceRootId(
-                                        0,
+                                    anchor: FileId(
+                                        1,
                                     ),
-                                    path: "foo.rs",
+                                    dst: "foo.rs",
                                 },
                             ],
                             is_snippet: false,
diff --git a/crates/ra_ide/src/display/navigation_target.rs b/crates/ra_ide/src/display/navigation_target.rs
index c7bb1e69f..0b52b01ab 100644
--- a/crates/ra_ide/src/display/navigation_target.rs
+++ b/crates/ra_ide/src/display/navigation_target.rs
@@ -135,8 +135,8 @@ impl NavigationTarget {
         db: &RootDatabase,
         node: InFile<&dyn ast::NameOwner>,
     ) -> NavigationTarget {
-        //FIXME: use `_` instead of empty string
-        let name = node.value.name().map(|it| it.text().clone()).unwrap_or_default();
+        let name =
+            node.value.name().map(|it| it.text().clone()).unwrap_or_else(|| SmolStr::new("_"));
         let focus_range =
             node.value.name().map(|it| original_range(db, node.with_value(it.syntax())).range);
         let frange = original_range(db, node.map(|it| it.syntax()));
@@ -150,6 +150,25 @@ impl NavigationTarget {
         )
     }
 
+    /// Allows `NavigationTarget` to be created from a `DocCommentsOwner` and a `NameOwner`
+    pub(crate) fn from_doc_commented(
+        db: &RootDatabase,
+        named: InFile<&dyn ast::NameOwner>,
+        node: InFile<&dyn ast::DocCommentsOwner>,
+    ) -> NavigationTarget {
+        let name =
+            named.value.name().map(|it| it.text().clone()).unwrap_or_else(|| SmolStr::new("_"));
+        let frange = original_range(db, node.map(|it| it.syntax()));
+
+        NavigationTarget::from_syntax(
+            frange.file_id,
+            name,
+            None,
+            frange.range,
+            node.value.syntax().kind(),
+        )
+    }
+
     fn from_syntax(
         file_id: FileId,
         name: SmolStr,
diff --git a/crates/ra_ide/src/hover.rs b/crates/ra_ide/src/hover.rs
index ad78b7671..d870e4cbc 100644
--- a/crates/ra_ide/src/hover.rs
+++ b/crates/ra_ide/src/hover.rs
@@ -2,7 +2,7 @@ use std::iter::once;
 
 use hir::{
     Adt, AsAssocItem, AssocItemContainer, Documentation, FieldSource, HasSource, HirDisplay,
-    ModuleDef, ModuleSource, Semantics,
+    Module, ModuleDef, ModuleSource, Semantics,
 };
 use itertools::Itertools;
 use ra_db::SourceDatabase;
@@ -13,7 +13,9 @@ use ra_ide_db::{
 use ra_syntax::{ast, match_ast, AstNode, SyntaxKind::*, SyntaxToken, TokenAtOffset};
 
 use crate::{
-    display::{macro_label, rust_code_markup, rust_code_markup_with_doc, ShortLabel, ToNav},
+    display::{
+        macro_label, rust_code_markup, rust_code_markup_with_doc, ShortLabel, ToNav, TryToNav,
+    },
     runnables::runnable,
     FileId, FilePosition, NavigationTarget, RangeInfo, Runnable,
 };
@@ -24,19 +26,21 @@ pub struct HoverConfig {
     pub implementations: bool,
     pub run: bool,
     pub debug: bool,
+    pub goto_type_def: bool,
 }
 
 impl Default for HoverConfig {
     fn default() -> Self {
-        Self { implementations: true, run: true, debug: true }
+        Self { implementations: true, run: true, debug: true, goto_type_def: true }
     }
 }
 
 impl HoverConfig {
-    pub const NO_ACTIONS: Self = Self { implementations: false, run: false, debug: false };
+    pub const NO_ACTIONS: Self =
+        Self { implementations: false, run: false, debug: false, goto_type_def: false };
 
     pub fn any(&self) -> bool {
-        self.implementations || self.runnable()
+        self.implementations || self.runnable() || self.goto_type_def
     }
 
     pub fn none(&self) -> bool {
@@ -52,6 +56,13 @@ impl HoverConfig {
 pub enum HoverAction {
     Runnable(Runnable),
     Implementaion(FilePosition),
+    GoToType(Vec<HoverGotoTypeData>),
+}
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct HoverGotoTypeData {
+    pub mod_path: String,
+    pub nav: NavigationTarget,
 }
 
 /// Contains the results when hovering over an item
@@ -138,6 +149,10 @@ pub(crate) fn hover(db: &RootDatabase, position: FilePosition) -> Option<RangeIn
                 res.push_action(action);
             }
 
+            if let Some(action) = goto_type_action(db, name_kind) {
+                res.push_action(action);
+            }
+
             return Some(RangeInfo::new(range, res));
         }
     }
@@ -218,6 +233,44 @@ fn runnable_action(
     }
 }
 
+fn goto_type_action(db: &RootDatabase, def: Definition) -> Option<HoverAction> {
+    match def {
+        Definition::Local(it) => {
+            let mut targets: Vec<ModuleDef> = Vec::new();
+            let mut push_new_def = |item: ModuleDef| {
+                if !targets.contains(&item) {
+                    targets.push(item);
+                }
+            };
+
+            it.ty(db).walk(db, |t| {
+                if let Some(adt) = t.as_adt() {
+                    push_new_def(adt.into());
+                } else if let Some(trait_) = t.as_dyn_trait() {
+                    push_new_def(trait_.into());
+                } else if let Some(traits) = t.as_impl_traits(db) {
+                    traits.into_iter().for_each(|it| push_new_def(it.into()));
+                } else if let Some(trait_) = t.as_associated_type_parent_trait(db) {
+                    push_new_def(trait_.into());
+                }
+            });
+
+            let targets = targets
+                .into_iter()
+                .filter_map(|it| {
+                    Some(HoverGotoTypeData {
+                        mod_path: mod_path(db, &it)?,
+                        nav: it.try_to_nav(db)?,
+                    })
+                })
+                .collect();
+
+            Some(HoverAction::GoToType(targets))
+        }
+        _ => None,
+    }
+}
+
 fn hover_text(
     docs: Option<String>,
     desc: Option<String>,
@@ -248,25 +301,31 @@ fn definition_owner_name(db: &RootDatabase, def: &Definition) -> Option<String>
     .map(|name| name.to_string())
 }
 
-fn determine_mod_path(db: &RootDatabase, def: &Definition) -> Option<String> {
-    let mod_path = def.module(db).map(|module| {
-        once(db.crate_graph()[module.krate().into()].display_name.as_ref().map(ToString::to_string))
-            .chain(
-                module
-                    .path_to_root(db)
-                    .into_iter()
-                    .rev()
-                    .map(|it| it.name(db).map(|name| name.to_string())),
-            )
-            .chain(once(definition_owner_name(db, def)))
-            .flatten()
-            .join("::")
-    });
-    mod_path
+fn determine_mod_path(db: &RootDatabase, module: Module, name: Option<String>) -> String {
+    once(db.crate_graph()[module.krate().into()].display_name.as_ref().map(ToString::to_string))
+        .chain(
+            module
+                .path_to_root(db)
+                .into_iter()
+                .rev()
+                .map(|it| it.name(db).map(|name| name.to_string())),
+        )
+        .chain(once(name))
+        .flatten()
+        .join("::")
+}
+
+// returns None only for ModuleDef::BuiltinType
+fn mod_path(db: &RootDatabase, item: &ModuleDef) -> Option<String> {
+    Some(determine_mod_path(db, item.module(db)?, item.name(db).map(|name| name.to_string())))
+}
+
+fn definition_mod_path(db: &RootDatabase, def: &Definition) -> Option<String> {
+    def.module(db).map(|module| determine_mod_path(db, module, definition_owner_name(db, def)))
 }
 
 fn hover_text_from_name_kind(db: &RootDatabase, def: Definition) -> Option<String> {
-    let mod_path = determine_mod_path(db, &def);
+    let mod_path = definition_mod_path(db, &def);
     return match def {
         Definition::Macro(it) => {
             let src = it.source(db);
@@ -1310,4 +1369,1045 @@ fn func(foo: i32) { if true { <|>foo; }; }
             ]
             "###);
     }
+
+    #[test]
+    fn test_hover_struct_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            struct S{ f1: u32 }
+
+            fn main() {
+                let s<|>t = S{ f1:0 };
+            }
+            ",
+            &["S"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "S",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..19,
+                                name: "S",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    7..8,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_generic_struct_has_goto_type_actions() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            struct Arg(u32);
+            struct S<T>{ f1: T }
+
+            fn main() {
+                let s<|>t = S{ f1:Arg(0) };
+            }
+            ",
+            &["S<Arg>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "S",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 17..37,
+                                name: "S",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    24..25,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "Arg",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..16,
+                                name: "Arg",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    7..10,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct Arg",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_generic_struct_has_flattened_goto_type_actions() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            struct Arg(u32);
+            struct S<T>{ f1: T }
+
+            fn main() {
+                let s<|>t = S{ f1: S{ f1: Arg(0) } };
+            }
+            ",
+            &["S<S<Arg>>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "S",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 17..37,
+                                name: "S",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    24..25,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "Arg",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..16,
+                                name: "Arg",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    7..10,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct Arg",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_tuple_has_goto_type_actions() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            struct A(u32);
+            struct B(u32);
+            mod M {
+                pub struct C(u32);
+            }
+
+            fn main() {
+                let s<|>t = (A(1), B(2), M::C(3) );
+            }
+            ",
+            &["(A, B, C)"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "A",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..14,
+                                name: "A",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    7..8,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct A",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "B",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 15..29,
+                                name: "B",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    22..23,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct B",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "M::C",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 42..60,
+                                name: "C",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    53..54,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "pub struct C",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+               "###);
+    }
+
+    #[test]
+    fn test_hover_return_impl_trait_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            trait Foo {}
+
+            fn foo() -> impl Foo {}
+
+            fn main() {
+                let s<|>t = foo();
+            }
+            ",
+            &["impl Foo"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..12,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_generic_return_impl_trait_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            trait Foo<T> {}
+            struct S;
+
+            fn foo() -> impl Foo<S> {}
+
+            fn main() {
+                let s<|>t = foo();
+            }
+            ",
+            &["impl Foo<S>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..15,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "S",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 16..25,
+                                name: "S",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    23..24,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_return_impl_traits_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            trait Foo {}
+            trait Bar {}
+
+            fn foo() -> impl Foo + Bar {}
+
+            fn main() {
+                let s<|>t = foo();
+            }
+            ",
+            &["impl Foo + Bar"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..12,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "Bar",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 13..25,
+                                name: "Bar",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    19..22,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Bar",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_generic_return_impl_traits_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            trait Foo<T> {}
+            trait Bar<T> {}
+            struct S1 {}
+            struct S2 {}
+
+            fn foo() -> impl Foo<S1> + Bar<S2> {}
+
+            fn main() {
+                let s<|>t = foo();
+            }
+            ",
+            &["impl Foo<S1> + Bar<S2>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..15,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "Bar",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 16..31,
+                                name: "Bar",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    22..25,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Bar",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "S1",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 32..44,
+                                name: "S1",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    39..41,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S1",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "S2",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 45..57,
+                                name: "S2",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    52..54,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S2",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+               "###);
+    }
+
+    #[test]
+    fn test_hover_arg_impl_trait_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /lib.rs
+            trait Foo {}
+            fn foo(ar<|>g: &impl Foo) {}
+            ",
+            &["&impl Foo"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..12,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_arg_impl_traits_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /lib.rs
+            trait Foo {}
+            trait Bar<T> {}
+            struct S{}
+
+            fn foo(ar<|>g: &impl Foo + Bar<S>) {}
+            ",
+            &["&impl Foo + Bar<S>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..12,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "Bar",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 13..28,
+                                name: "Bar",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    19..22,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Bar",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "S",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 29..39,
+                                name: "S",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    36..37,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_arg_generic_impl_trait_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /lib.rs
+            trait Foo<T> {}
+            struct S {}
+            fn foo(ar<|>g: &impl Foo<S>) {}
+            ",
+            &["&impl Foo<S>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..15,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "S",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 16..27,
+                                name: "S",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    23..24,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_dyn_return_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            trait Foo {}
+            struct S;
+            impl Foo for S {}
+
+            struct B<T>{}
+
+            fn foo() -> B<dyn Foo> {}
+
+            fn main() {
+                let s<|>t = foo();
+            }
+            ",
+            &["B<dyn Foo>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "B",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 41..54,
+                                name: "B",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    48..49,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct B",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..12,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_dyn_arg_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /lib.rs
+            trait Foo {}
+            fn foo(ar<|>g: &dyn Foo) {}
+            ",
+            &["&dyn Foo"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..12,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_generic_dyn_arg_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /lib.rs
+            trait Foo<T> {}
+            struct S {}
+            fn foo(ar<|>g: &dyn Foo<S>) {}
+            ",
+            &["&dyn Foo<S>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..15,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "S",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 16..27,
+                                name: "S",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    23..24,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_goto_type_action_links_order() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /lib.rs
+            trait ImplTrait<T> {}
+            trait DynTrait<T> {}
+            struct B<T> {}
+            struct S {}
+
+            fn foo(a<|>rg: &impl ImplTrait<B<dyn DynTrait<B<S>>>>) {}
+            ",
+            &["&impl ImplTrait<B<dyn DynTrait<B<S>>>>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "ImplTrait",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..21,
+                                name: "ImplTrait",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..15,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait ImplTrait",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "B",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 43..57,
+                                name: "B",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    50..51,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct B",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "DynTrait",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 22..42,
+                                name: "DynTrait",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    28..36,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait DynTrait",
+                                ),
+                                docs: None,
+                            },
+                        },
+                        HoverGotoTypeData {
+                            mod_path: "S",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 58..69,
+                                name: "S",
+                                kind: STRUCT_DEF,
+                                focus_range: Some(
+                                    65..66,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "struct S",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
+
+    #[test]
+    fn test_hover_associated_type_has_goto_type_action() {
+        let (_, actions) = check_hover_result(
+            "
+            //- /main.rs
+            trait Foo {
+                type Item;
+                fn get(self) -> Self::Item {}
+            }
+
+            struct Bar{}
+            struct S{}
+
+            impl Foo for S{
+                type Item = Bar;
+            }
+
+            fn test() -> impl Foo {
+                S{}
+            }
+
+            fn main() {
+                let s<|>t = test().get();
+            }
+            ",
+            &["Foo::Item<impl Foo>"],
+        );
+        assert_debug_snapshot!(actions,
+            @r###"
+            [
+                GoToType(
+                    [
+                        HoverGotoTypeData {
+                            mod_path: "Foo",
+                            nav: NavigationTarget {
+                                file_id: FileId(
+                                    1,
+                                ),
+                                full_range: 0..62,
+                                name: "Foo",
+                                kind: TRAIT_DEF,
+                                focus_range: Some(
+                                    6..9,
+                                ),
+                                container_name: None,
+                                description: Some(
+                                    "trait Foo",
+                                ),
+                                docs: None,
+                            },
+                        },
+                    ],
+                ),
+            ]
+            "###);
+    }
 }
diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index 28f686767..be9ab62c0 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -66,7 +66,7 @@ pub use crate::{
     display::{file_structure, FunctionSignature, NavigationTarget, StructureNode},
     expand_macro::ExpandedMacro,
     folding_ranges::{Fold, FoldKind},
-    hover::{HoverAction, HoverConfig, HoverResult},
+    hover::{HoverAction, HoverConfig, HoverGotoTypeData, HoverResult},
     inlay_hints::{InlayHint, InlayHintsConfig, InlayKind},
     references::{Declaration, Reference, ReferenceAccess, ReferenceKind, ReferenceSearchResult},
     runnables::{Runnable, RunnableKind, TestId},
@@ -82,7 +82,7 @@ pub use ra_db::{
     Canceled, CrateGraph, CrateId, Edition, FileId, FilePosition, FileRange, SourceRootId,
 };
 pub use ra_ide_db::{
-    change::{AnalysisChange, LibraryData},
+    change::AnalysisChange,
     line_index::{LineCol, LineIndex},
     search::SearchScope,
     source_change::{FileSystemEdit, SourceChange, SourceFileEdit},
@@ -440,12 +440,14 @@ impl Analysis {
 
     /// Computes syntax highlighting for the given file
     pub fn highlight(&self, file_id: FileId) -> Cancelable<Vec<HighlightedRange>> {
-        self.with_db(|db| syntax_highlighting::highlight(db, file_id, None))
+        self.with_db(|db| syntax_highlighting::highlight(db, file_id, None, false))
     }
 
     /// Computes syntax highlighting for the given file range.
     pub fn highlight_range(&self, frange: FileRange) -> Cancelable<Vec<HighlightedRange>> {
-        self.with_db(|db| syntax_highlighting::highlight(db, frange.file_id, Some(frange.range)))
+        self.with_db(|db| {
+            syntax_highlighting::highlight(db, frange.file_id, Some(frange.range), false)
+        })
     }
 
     /// Computes syntax highlighting for the given file.
diff --git a/crates/ra_ide/src/prime_caches.rs b/crates/ra_ide/src/prime_caches.rs
index 90bf7d25f..c5ab5a1d8 100644
--- a/crates/ra_ide/src/prime_caches.rs
+++ b/crates/ra_ide/src/prime_caches.rs
@@ -7,6 +7,6 @@ use crate::{FileId, RootDatabase};
 
 pub(crate) fn prime_caches(db: &RootDatabase, files: Vec<FileId>) {
     for file in files {
-        let _ = crate::syntax_highlighting::highlight(db, file, None);
+        let _ = crate::syntax_highlighting::highlight(db, file, None, false);
     }
 }
diff --git a/crates/ra_ide/src/references/rename.rs b/crates/ra_ide/src/references/rename.rs
index 915d4f4d3..c4f07f905 100644
--- a/crates/ra_ide/src/references/rename.rs
+++ b/crates/ra_ide/src/references/rename.rs
@@ -1,7 +1,7 @@
 //! FIXME: write short doc here
 
 use hir::{ModuleSource, Semantics};
-use ra_db::{RelativePath, RelativePathBuf, SourceDatabaseExt};
+use ra_db::{RelativePathBuf, SourceDatabaseExt};
 use ra_ide_db::RootDatabase;
 use ra_syntax::{
     algo::find_node_at_offset, ast, ast::TypeAscriptionOwner, lex_single_valid_syntax_kind,
@@ -92,23 +92,14 @@ fn rename_mod(
             ModuleSource::SourceFile(..) => {
                 let mod_path: RelativePathBuf = sema.db.file_relative_path(file_id);
                 // mod is defined in path/to/dir/mod.rs
-                let dst_path = if mod_path.file_stem() == Some("mod") {
-                    mod_path
-                        .parent()
-                        .and_then(|p| p.parent())
-                        .or_else(|| Some(RelativePath::new("")))
-                        .map(|p| p.join(new_name).join("mod.rs"))
+                let dst = if mod_path.file_stem() == Some("mod") {
+                    format!("../{}/mod.rs", new_name)
                 } else {
-                    Some(mod_path.with_file_name(new_name).with_extension("rs"))
+                    format!("{}.rs", new_name)
                 };
-                if let Some(path) = dst_path {
-                    let move_file = FileSystemEdit::MoveFile {
-                        src: file_id,
-                        dst_source_root: sema.db.file_source_root(position.file_id),
-                        dst_path: path,
-                    };
-                    file_system_edits.push(move_file);
-                }
+                let move_file =
+                    FileSystemEdit::MoveFile { src: file_id, anchor: position.file_id, dst };
+                file_system_edits.push(move_file);
             }
             ModuleSource::Module(..) => {}
         }
@@ -623,16 +614,16 @@ mod tests {
     #[test]
     fn test_rename_mod() {
         let (analysis, position) = analysis_and_position(
-            "
-            //- /lib.rs
-            mod bar;
+            r#"
+//- /lib.rs
+mod bar;
 
-            //- /bar.rs
-            mod foo<|>;
+//- /bar.rs
+mod foo<|>;
 
-            //- /bar/foo.rs
-            // emtpy
-            ",
+//- /bar/foo.rs
+// emtpy
+            "#,
         );
         let new_name = "foo2";
         let source_change = analysis.rename(position, new_name).unwrap();
@@ -662,10 +653,10 @@ mod tests {
                             src: FileId(
                                 3,
                             ),
-                            dst_source_root: SourceRootId(
-                                0,
+                            anchor: FileId(
+                                2,
                             ),
-                            dst_path: "bar/foo2.rs",
+                            dst: "foo2.rs",
                         },
                     ],
                     is_snippet: false,
@@ -678,12 +669,12 @@ mod tests {
     #[test]
     fn test_rename_mod_in_dir() {
         let (analysis, position) = analysis_and_position(
-            "
-            //- /lib.rs
-            mod fo<|>o;
-            //- /foo/mod.rs
-            // emtpy
-            ",
+            r#"
+//- /lib.rs
+mod fo<|>o;
+//- /foo/mod.rs
+// emtpy
+            "#,
         );
         let new_name = "foo2";
         let source_change = analysis.rename(position, new_name).unwrap();
@@ -713,10 +704,10 @@ mod tests {
                             src: FileId(
                                 2,
                             ),
-                            dst_source_root: SourceRootId(
-                                0,
+                            anchor: FileId(
+                                1,
                             ),
-                            dst_path: "foo2/mod.rs",
+                            dst: "../foo2/mod.rs",
                         },
                     ],
                     is_snippet: false,
@@ -753,19 +744,19 @@ mod tests {
     #[test]
     fn test_rename_mod_filename_and_path() {
         let (analysis, position) = analysis_and_position(
-            "
-            //- /lib.rs
-            mod bar;
-            fn f() {
-                bar::foo::fun()
-            }
+            r#"
+//- /lib.rs
+mod bar;
+fn f() {
+    bar::foo::fun()
+}
 
-            //- /bar.rs
-            pub mod foo<|>;
+//- /bar.rs
+pub mod foo<|>;
 
-            //- /bar/foo.rs
-            // pub fn fun() {}
-            ",
+//- /bar/foo.rs
+// pub fn fun() {}
+            "#,
         );
         let new_name = "foo2";
         let source_change = analysis.rename(position, new_name).unwrap();
@@ -808,10 +799,10 @@ mod tests {
                             src: FileId(
                                 3,
                             ),
-                            dst_source_root: SourceRootId(
-                                0,
+                            anchor: FileId(
+                                2,
                             ),
-                            dst_path: "bar/foo2.rs",
+                            dst: "foo2.rs",
                         },
                     ],
                     is_snippet: false,
diff --git a/crates/ra_ide/src/runnables.rs b/crates/ra_ide/src/runnables.rs
index fc57dc33d..8105ef373 100644
--- a/crates/ra_ide/src/runnables.rs
+++ b/crates/ra_ide/src/runnables.rs
@@ -171,7 +171,15 @@ fn runnable_fn(
     let cfg_exprs =
         attrs.by_key("cfg").tt_values().map(|subtree| ra_cfg::parse_cfg(subtree)).collect();
 
-    let nav = NavigationTarget::from_named(sema.db, InFile::new(file_id.into(), &fn_def));
+    let nav = if let RunnableKind::DocTest { .. } = kind {
+        NavigationTarget::from_doc_commented(
+            sema.db,
+            InFile::new(file_id.into(), &fn_def),
+            InFile::new(file_id.into(), &fn_def),
+        )
+    } else {
+        NavigationTarget::from_named(sema.db, InFile::new(file_id.into(), &fn_def))
+    };
     Some(Runnable { nav, kind, cfg_exprs })
 }
 
@@ -419,9 +427,7 @@ mod tests {
                     full_range: 22..64,
                     name: "foo",
                     kind: FN_DEF,
-                    focus_range: Some(
-                        56..59,
-                    ),
+                    focus_range: None,
                     container_name: None,
                     description: None,
                     docs: None,
@@ -486,9 +492,7 @@ mod tests {
                     full_range: 51..105,
                     name: "foo",
                     kind: FN_DEF,
-                    focus_range: Some(
-                        97..100,
-                    ),
+                    focus_range: None,
                     container_name: None,
                     description: None,
                     docs: None,
diff --git a/crates/ra_ide/src/snapshots/highlight_doctest.html b/crates/ra_ide/src/snapshots/highlight_doctest.html
index 0ae8c7efc..f61c0daa5 100644
--- a/crates/ra_ide/src/snapshots/highlight_doctest.html
+++ b/crates/ra_ide/src/snapshots/highlight_doctest.html
@@ -25,46 +25,62 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .variable           { color: #DCDCCC; }
 .format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
+.unresolved_reference { color: #FC5555; }
+.escape_sequence    { color: #94BFF3; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
 .keyword.unsafe     { color: #BC8383; font-weight: bold; }
 .control            { font-style: italic; }
 </style>
-<pre><code><span class="keyword">impl</span> <span class="unresolved_reference">Foo</span> {
-    <span class="comment">/// Constructs a new `Foo`.</span>
-    <span class="comment">///</span>
-    <span class="comment">/// # Examples</span>
-    <span class="comment">///</span>
-    <span class="comment">/// ```</span>
-    <span class="comment">/// #</span> <span class="attribute">#![</span><span class="function attribute">allow</span><span class="attribute">(unused_mut)]</span>
-    <span class="comment">/// </span><span class="keyword">let</span> <span class="keyword">mut</span> <span class="variable declaration mutable">foo</span>: <span class="unresolved_reference">Foo</span> = <span class="unresolved_reference">Foo</span>::<span class="unresolved_reference">new</span>();
-    <span class="comment">/// ```</span>
-    <span class="keyword">pub</span> <span class="keyword">const</span> <span class="keyword">fn</span> <span class="function declaration">new</span>() -&gt; <span class="unresolved_reference">Foo</span> {
-        <span class="unresolved_reference">Foo</span> { }
+<pre><code><span class="keyword">struct</span> <span class="struct declaration">Foo</span> {
+    <span class="field declaration">bar</span>: <span class="builtin_type">bool</span>,
+}
+
+<span class="keyword">impl</span> <span class="struct">Foo</span> {
+    <span class="keyword">pub</span> <span class="keyword">const</span> <span class="constant declaration">bar</span>: <span class="builtin_type">bool</span> = <span class="bool_literal">true</span>;
+
+    <span class="comment documentation">/// Constructs a new `Foo`.</span>
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// # Examples</span>
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// ```</span>
+    <span class="comment documentation">/// #</span> <span class="attribute">#![</span><span class="function attribute">allow</span><span class="attribute">(unused_mut)]</span>
+    <span class="comment documentation">/// </span><span class="keyword">let</span> <span class="keyword">mut</span> <span class="variable declaration mutable">foo</span>: <span class="struct">Foo</span> = <span class="struct">Foo</span>::<span class="function">new</span>();
+    <span class="comment documentation">/// ```</span>
+    <span class="keyword">pub</span> <span class="keyword">const</span> <span class="keyword">fn</span> <span class="function declaration">new</span>() -&gt; <span class="struct">Foo</span> {
+        <span class="struct">Foo</span> { <span class="field">bar</span>: <span class="bool_literal">true</span> }
     }
 
-    <span class="comment">/// `bar` method on `Foo`.</span>
-    <span class="comment">///</span>
-    <span class="comment">/// # Examples</span>
-    <span class="comment">///</span>
-    <span class="comment">/// ```</span>
-    <span class="comment">/// </span><span class="keyword">let</span> <span class="variable declaration">foo</span> = <span class="unresolved_reference">Foo</span>::<span class="unresolved_reference">new</span>();
-    <span class="comment">///</span>
-    <span class="comment">/// </span><span class="comment">// calls bar on foo</span>
-    <span class="comment">/// </span><span class="macro">assert!</span>(foo.bar());
-    <span class="comment">///</span>
-    <span class="comment">/// </span><span class="comment">/* multi-line
-    </span><span class="comment">/// </span><span class="comment">       comment */</span>
-    <span class="comment">///</span>
-    <span class="comment">/// </span><span class="keyword">let</span> <span class="variable declaration">multi_line_string</span> = <span class="string_literal">"Foo
-    </span><span class="comment">/// </span><span class="string_literal">  bar
-    </span><span class="comment">/// </span><span class="string_literal">         "</span>;
-    <span class="comment">///</span>
-    <span class="comment">/// ```</span>
-    <span class="comment">///</span>
-    <span class="comment">/// ```</span>
-    <span class="comment">/// </span><span class="keyword">let</span> <span class="variable declaration">foobar</span> = <span class="unresolved_reference">Foo</span>::<span class="unresolved_reference">new</span>().<span class="unresolved_reference">bar</span>();
-    <span class="comment">/// ```</span>
+    <span class="comment documentation">/// `bar` method on `Foo`.</span>
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// # Examples</span>
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// ```</span>
+    <span class="comment documentation">/// </span><span class="keyword">use</span> <span class="module">x</span>::<span class="module">y</span>;
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// </span><span class="keyword">let</span> <span class="variable declaration">foo</span> = <span class="struct">Foo</span>::<span class="function">new</span>();
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// </span><span class="comment">// calls bar on foo</span>
+    <span class="comment documentation">/// </span><span class="macro">assert!</span>(foo.bar());
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// </span><span class="keyword">let</span> <span class="variable declaration">bar</span> = <span class="variable">foo</span>.<span class="field">bar</span> || <span class="struct">Foo</span>::<span class="constant">bar</span>;
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// </span><span class="comment">/* multi-line
+    </span><span class="comment documentation">/// </span><span class="comment">       comment */</span>
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// </span><span class="keyword">let</span> <span class="variable declaration">multi_line_string</span> = <span class="string_literal">"Foo
+    </span><span class="comment documentation">/// </span><span class="string_literal">  bar
+    </span><span class="comment documentation">/// </span><span class="string_literal">         "</span>;
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// ```</span>
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// ```rust,no_run</span>
+    <span class="comment documentation">/// </span><span class="keyword">let</span> <span class="variable declaration">foobar</span> = <span class="struct">Foo</span>::<span class="function">new</span>().<span class="function">bar</span>();
+    <span class="comment documentation">/// ```</span>
+    <span class="comment documentation">///</span>
+    <span class="comment documentation">/// ```sh</span>
+    <span class="comment documentation">/// echo 1</span>
+    <span class="comment documentation">/// ```</span>
     <span class="keyword">pub</span> <span class="keyword">fn</span> <span class="function declaration">foo</span>(&<span class="self_keyword">self</span>) -&gt; <span class="builtin_type">bool</span> {
         <span class="bool_literal">true</span>
     }
diff --git a/crates/ra_ide/src/snapshots/highlight_injection.html b/crates/ra_ide/src/snapshots/highlight_injection.html
index dec06eb51..47dbd7bc8 100644
--- a/crates/ra_ide/src/snapshots/highlight_injection.html
+++ b/crates/ra_ide/src/snapshots/highlight_injection.html
@@ -25,6 +25,8 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .variable           { color: #DCDCCC; }
 .format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
+.unresolved_reference { color: #FC5555; }
+.escape_sequence    { color: #94BFF3; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
 .keyword.unsafe     { color: #BC8383; font-weight: bold; }
diff --git a/crates/ra_ide/src/snapshots/highlight_strings.html b/crates/ra_ide/src/snapshots/highlight_strings.html
index 849eb3b73..b46fa44c6 100644
--- a/crates/ra_ide/src/snapshots/highlight_strings.html
+++ b/crates/ra_ide/src/snapshots/highlight_strings.html
@@ -25,6 +25,8 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .variable           { color: #DCDCCC; }
 .format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
+.unresolved_reference { color: #FC5555; }
+.escape_sequence    { color: #94BFF3; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
 .keyword.unsafe     { color: #BC8383; font-weight: bold; }
@@ -82,6 +84,10 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 
     <span class="macro">println!</span>(<span class="string_literal">r"Hello, </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"world"</span>);
 
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="variable">\x41</span><span class="format_specifier">}</span><span class="string_literal">"</span>, A = <span class="numeric_literal">92</span>);
+    <span class="comment">// escape sequences</span>
+    <span class="macro">println!</span>(<span class="string_literal">"Hello</span><span class="escape_sequence">\n</span><span class="string_literal">World"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="escape_sequence">\u{48}</span><span class="escape_sequence">\x65</span><span class="escape_sequence">\x6C</span><span class="escape_sequence">\x6C</span><span class="escape_sequence">\x6F</span><span class="string_literal"> World"</span>);
+
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="escape_sequence">\x41</span><span class="format_specifier">}</span><span class="string_literal">"</span>, A = <span class="numeric_literal">92</span>);
     <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="variable">ничоси</span><span class="format_specifier">}</span><span class="string_literal">"</span>, ничоси = <span class="numeric_literal">92</span>);
 }</code></pre>
\ No newline at end of file
diff --git a/crates/ra_ide/src/snapshots/highlight_unsafe.html b/crates/ra_ide/src/snapshots/highlight_unsafe.html
index bd24e6e38..73438fbb4 100644
--- a/crates/ra_ide/src/snapshots/highlight_unsafe.html
+++ b/crates/ra_ide/src/snapshots/highlight_unsafe.html
@@ -25,6 +25,8 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .variable           { color: #DCDCCC; }
 .format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
+.unresolved_reference { color: #FC5555; }
+.escape_sequence    { color: #94BFF3; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
 .keyword.unsafe     { color: #BC8383; font-weight: bold; }
diff --git a/crates/ra_ide/src/snapshots/highlighting.html b/crates/ra_ide/src/snapshots/highlighting.html
index 33548d43c..0c4f0a018 100644
--- a/crates/ra_ide/src/snapshots/highlighting.html
+++ b/crates/ra_ide/src/snapshots/highlighting.html
@@ -25,6 +25,8 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .variable           { color: #DCDCCC; }
 .format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
+.unresolved_reference { color: #FC5555; }
+.escape_sequence    { color: #94BFF3; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
 .keyword.unsafe     { color: #BC8383; font-weight: bold; }
@@ -62,6 +64,12 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     }
 }
 
+<span class="macro">macro_rules!</span> <span class="macro declaration">noop</span> {
+    ($expr:expr) =&gt; {
+        $expr
+    }
+}
+
 <span class="comment">// comment</span>
 <span class="keyword">fn</span> <span class="function declaration">main</span>() {
     <span class="macro">println!</span>(<span class="string_literal">"Hello, {}!"</span>, <span class="numeric_literal">92</span>);
@@ -80,6 +88,8 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
         <span class="comment">// Do nothing</span>
     }
 
+    <span class="macro">noop!</span>(<span class="macro">noop</span><span class="macro">!</span>(<span class="numeric_literal">1</span>));
+
     <span class="keyword">let</span> <span class="keyword">mut</span> <span class="variable declaration mutable">x</span> = <span class="numeric_literal">42</span>;
     <span class="keyword">let</span> <span class="variable declaration mutable">y</span> = &<span class="keyword">mut</span> <span class="variable mutable">x</span>;
     <span class="keyword">let</span> <span class="variable declaration">z</span> = &<span class="variable mutable">y</span>;
diff --git a/crates/ra_ide/src/snapshots/rainbow_highlighting.html b/crates/ra_ide/src/snapshots/rainbow_highlighting.html
index 1ab06182c..a74a70069 100644
--- a/crates/ra_ide/src/snapshots/rainbow_highlighting.html
+++ b/crates/ra_ide/src/snapshots/rainbow_highlighting.html
@@ -25,6 +25,8 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .variable           { color: #DCDCCC; }
 .format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
+.unresolved_reference { color: #FC5555; }
+.escape_sequence    { color: #94BFF3; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
 .keyword.unsafe     { color: #BC8383; font-weight: bold; }
diff --git a/crates/ra_ide/src/ssr.rs b/crates/ra_ide/src/ssr.rs
index 93e9aee1d..762aab962 100644
--- a/crates/ra_ide/src/ssr.rs
+++ b/crates/ra_ide/src/ssr.rs
@@ -27,11 +27,11 @@ impl std::error::Error for SsrError {}
 //
 // Search and replace with named wildcards that will match any expression.
 // The syntax for a structural search replace command is `<search_pattern> ==>> <replace_pattern>`.
-// A `$<name>:expr` placeholder in the search pattern will match any expression and `$<name>` will reference it in the replacement.
+// A `$<name>` placeholder in the search pattern will match any AST node and `$<name>` will reference it in the replacement.
 // Available via the command `rust-analyzer.ssr`.
 //
 // ```rust
-// // Using structural search replace command [foo($a:expr, $b:expr) ==>> ($a).foo($b)]
+// // Using structural search replace command [foo($a, $b) ==>> ($a).foo($b)]
 //
 // // BEFORE
 // String::from(foo(y + 5, z))
@@ -79,7 +79,7 @@ struct SsrPattern {
     vars: Vec<Var>,
 }
 
-/// represents an `$var` in an SSR query
+/// Represents a `$var` in an SSR query.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 struct Var(String);
 
@@ -122,8 +122,7 @@ impl FromStr for SsrQuery {
         let mut pattern = it.next().expect("something").to_string();
 
         for part in it.map(split_by_var) {
-            let (var, var_type, remainder) = part?;
-            is_expr(var_type)?;
+            let (var, remainder) = part?;
             let new_var = create_name(var, &mut vars)?;
             pattern.push_str(new_var);
             pattern.push_str(remainder);
@@ -166,15 +165,11 @@ fn traverse(node: &SyntaxNode, go: &mut impl FnMut(&SyntaxNode) -> bool) {
     }
 }
 
-fn split_by_var(s: &str) -> Result<(&str, &str, &str), SsrError> {
-    let end_of_name = s.find(':').ok_or_else(|| SsrError("Use $<name>:expr".into()))?;
-    let name = &s[0..end_of_name];
+fn split_by_var(s: &str) -> Result<(&str, &str), SsrError> {
+    let end_of_name = s.find(|c| !char::is_ascii_alphanumeric(&c)).unwrap_or_else(|| s.len());
+    let name = &s[..end_of_name];
     is_name(name)?;
-    let type_begin = end_of_name + 1;
-    let type_length =
-        s[type_begin..].find(|c| !char::is_ascii_alphanumeric(&c)).unwrap_or_else(|| s.len());
-    let type_name = &s[type_begin..type_begin + type_length];
-    Ok((name, type_name, &s[type_begin + type_length..]))
+    Ok((name, &s[end_of_name..]))
 }
 
 fn is_name(s: &str) -> Result<(), SsrError> {
@@ -185,14 +180,6 @@ fn is_name(s: &str) -> Result<(), SsrError> {
     }
 }
 
-fn is_expr(s: &str) -> Result<(), SsrError> {
-    if s == "expr" {
-        Ok(())
-    } else {
-        Err(SsrError("Only $<name>:expr is supported".into()))
-    }
-}
-
 fn replace_in_template(template: String, var: &str, new_var: &str) -> String {
     let name = format!("${}", var);
     template.replace(&name, new_var)
@@ -450,7 +437,7 @@ mod tests {
 
     #[test]
     fn parser_happy_case() {
-        let result: SsrQuery = "foo($a:expr, $b:expr) ==>> bar($b, $a)".parse().unwrap();
+        let result: SsrQuery = "foo($a, $b) ==>> bar($b, $a)".parse().unwrap();
         assert_eq!(&result.pattern.pattern.text(), "foo(__search_pattern_a, __search_pattern_b)");
         assert_eq!(result.pattern.vars.len(), 2);
         assert_eq!(result.pattern.vars[0].0, "__search_pattern_a");
@@ -477,30 +464,9 @@ mod tests {
     }
 
     #[test]
-    fn parser_no_pattern_type() {
-        assert_eq!(parse_error_text("foo($a) ==>>"), "Parse error: Use $<name>:expr");
-    }
-
-    #[test]
-    fn parser_invalid_name() {
-        assert_eq!(
-            parse_error_text("foo($a+:expr) ==>>"),
-            "Parse error: Name can contain only alphanumerics and _"
-        );
-    }
-
-    #[test]
-    fn parser_invalid_type() {
-        assert_eq!(
-            parse_error_text("foo($a:ident) ==>>"),
-            "Parse error: Only $<name>:expr is supported"
-        );
-    }
-
-    #[test]
     fn parser_repeated_name() {
         assert_eq!(
-            parse_error_text("foo($a:expr, $a:expr) ==>>"),
+            parse_error_text("foo($a, $a) ==>>"),
             "Parse error: Name `a` repeats more than once"
         );
     }
@@ -517,7 +483,7 @@ mod tests {
 
     #[test]
     fn parse_match_replace() {
-        let query: SsrQuery = "foo($x:expr) ==>> bar($x)".parse().unwrap();
+        let query: SsrQuery = "foo($x) ==>> bar($x)".parse().unwrap();
         let input = "fn main() { foo(1+2); }";
 
         let code = SourceFile::parse(input).tree();
@@ -549,7 +515,7 @@ mod tests {
     #[test]
     fn ssr_function_to_method() {
         assert_ssr_transform(
-            "my_function($a:expr, $b:expr) ==>> ($a).my_method($b)",
+            "my_function($a, $b) ==>> ($a).my_method($b)",
             "loop { my_function( other_func(x, y), z + w) }",
             "loop { (other_func(x, y)).my_method(z + w) }",
         )
@@ -558,7 +524,7 @@ mod tests {
     #[test]
     fn ssr_nested_function() {
         assert_ssr_transform(
-            "foo($a:expr, $b:expr, $c:expr) ==>> bar($c, baz($a, $b))",
+            "foo($a, $b, $c) ==>> bar($c, baz($a, $b))",
             "fn main { foo  (x + value.method(b), x+y-z, true && false) }",
             "fn main { bar(true && false, baz(x + value.method(b), x+y-z)) }",
         )
@@ -567,7 +533,7 @@ mod tests {
     #[test]
     fn ssr_expected_spacing() {
         assert_ssr_transform(
-            "foo($x:expr) + bar() ==>> bar($x)",
+            "foo($x) + bar() ==>> bar($x)",
             "fn main() { foo(5) + bar() }",
             "fn main() { bar(5) }",
         );
@@ -576,7 +542,7 @@ mod tests {
     #[test]
     fn ssr_with_extra_space() {
         assert_ssr_transform(
-            "foo($x:expr  ) +    bar() ==>> bar($x)",
+            "foo($x  ) +    bar() ==>> bar($x)",
             "fn main() { foo(  5 )  +bar(   ) }",
             "fn main() { bar(5) }",
         );
@@ -585,7 +551,7 @@ mod tests {
     #[test]
     fn ssr_keeps_nested_comment() {
         assert_ssr_transform(
-            "foo($x:expr) ==>> bar($x)",
+            "foo($x) ==>> bar($x)",
             "fn main() { foo(other(5 /* using 5 */)) }",
             "fn main() { bar(other(5 /* using 5 */)) }",
         )
@@ -594,7 +560,7 @@ mod tests {
     #[test]
     fn ssr_keeps_comment() {
         assert_ssr_transform(
-            "foo($x:expr) ==>> bar($x)",
+            "foo($x) ==>> bar($x)",
             "fn main() { foo(5 /* using 5 */) }",
             "fn main() { bar(5)/* using 5 */ }",
         )
@@ -603,7 +569,7 @@ mod tests {
     #[test]
     fn ssr_struct_lit() {
         assert_ssr_transform(
-            "foo{a: $a:expr, b: $b:expr} ==>> foo::new($a, $b)",
+            "foo{a: $a, b: $b} ==>> foo::new($a, $b)",
             "fn main() { foo{b:2, a:1} }",
             "fn main() { foo::new(1, 2) }",
         )
@@ -612,7 +578,7 @@ mod tests {
     #[test]
     fn ssr_call_and_method_call() {
         assert_ssr_transform(
-            "foo::<'a>($a:expr, $b:expr)) ==>> foo2($a, $b)",
+            "foo::<'a>($a, $b)) ==>> foo2($a, $b)",
             "fn main() { get().bar.foo::<'a>(1); }",
             "fn main() { foo2(get().bar, 1); }",
         )
@@ -621,7 +587,7 @@ mod tests {
     #[test]
     fn ssr_method_call_and_call() {
         assert_ssr_transform(
-            "$o:expr.foo::<i32>($a:expr)) ==>> $o.foo2($a)",
+            "$o.foo::<i32>($a)) ==>> $o.foo2($a)",
             "fn main() { X::foo::<i32>(x, 1); }",
             "fn main() { x.foo2(1); }",
         )
diff --git a/crates/ra_ide/src/status.rs b/crates/ra_ide/src/status.rs
index 5b7992920..45411b357 100644
--- a/crates/ra_ide/src/status.rs
+++ b/crates/ra_ide/src/status.rs
@@ -16,6 +16,7 @@ use ra_prof::{memory_usage, Bytes};
 use ra_syntax::{ast, Parse, SyntaxNode};
 
 use crate::FileId;
+use rustc_hash::FxHashMap;
 
 fn syntax_tree_stats(db: &RootDatabase) -> SyntaxTreeStats {
     db.query(ra_db::ParseQuery).entries::<SyntaxTreeStats>()
@@ -123,20 +124,24 @@ struct LibrarySymbolsStats {
 
 impl fmt::Display for LibrarySymbolsStats {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "{} ({}) symbols", self.total, self.size,)
+        write!(fmt, "{} ({}) symbols", self.total, self.size)
     }
 }
 
-impl FromIterator<TableEntry<SourceRootId, Arc<SymbolIndex>>> for LibrarySymbolsStats {
+impl FromIterator<TableEntry<(), Arc<FxHashMap<SourceRootId, SymbolIndex>>>>
+    for LibrarySymbolsStats
+{
     fn from_iter<T>(iter: T) -> LibrarySymbolsStats
     where
-        T: IntoIterator<Item = TableEntry<SourceRootId, Arc<SymbolIndex>>>,
+        T: IntoIterator<Item = TableEntry<(), Arc<FxHashMap<SourceRootId, SymbolIndex>>>>,
     {
         let mut res = LibrarySymbolsStats::default();
         for entry in iter {
             let value = entry.value.unwrap();
-            res.total += value.len();
-            res.size += value.memory_size();
+            for symbols in value.values() {
+                res.total += symbols.len();
+                res.size += symbols.memory_size();
+            }
         }
         res
     }
diff --git a/crates/ra_ide/src/syntax_highlighting.rs b/crates/ra_ide/src/syntax_highlighting.rs
index ab45c364a..f8f790e59 100644
--- a/crates/ra_ide/src/syntax_highlighting.rs
+++ b/crates/ra_ide/src/syntax_highlighting.rs
@@ -44,6 +44,7 @@ pub(crate) fn highlight(
     db: &RootDatabase,
     file_id: FileId,
     range_to_highlight: Option<TextRange>,
+    syntactic_name_ref_highlighting: bool,
 ) -> Vec<HighlightedRange> {
     let _p = profile("highlight");
     let sema = Semantics::new(db);
@@ -104,6 +105,7 @@ pub(crate) fn highlight(
                     if let Some((highlight, binding_hash)) = highlight_element(
                         &sema,
                         &mut bindings_shadow_count,
+                        syntactic_name_ref_highlighting,
                         name.syntax().clone().into(),
                     ) {
                         stack.add(HighlightedRange {
@@ -160,23 +162,25 @@ pub(crate) fn highlight(
             // Check if macro takes a format string and remember it for highlighting later.
             // The macros that accept a format string expand to a compiler builtin macros
             // `format_args` and `format_args_nl`.
-            if let Some(fmt_macro_call) = parent.parent().and_then(ast::MacroCall::cast) {
-                if let Some(name) =
-                    fmt_macro_call.path().and_then(|p| p.segment()).and_then(|s| s.name_ref())
-                {
-                    match name.text().as_str() {
-                        "format_args" | "format_args_nl" => {
-                            format_string = parent
-                                .children_with_tokens()
-                                .filter(|t| t.kind() != WHITESPACE)
-                                .nth(1)
-                                .filter(|e| {
-                                    ast::String::can_cast(e.kind())
-                                        || ast::RawString::can_cast(e.kind())
-                                })
-                        }
-                        _ => {}
+            if let Some(name) = parent
+                .parent()
+                .and_then(ast::MacroCall::cast)
+                .and_then(|mc| mc.path())
+                .and_then(|p| p.segment())
+                .and_then(|s| s.name_ref())
+            {
+                match name.text().as_str() {
+                    "format_args" | "format_args_nl" => {
+                        format_string = parent
+                            .children_with_tokens()
+                            .filter(|t| t.kind() != WHITESPACE)
+                            .nth(1)
+                            .filter(|e| {
+                                ast::String::can_cast(e.kind())
+                                    || ast::RawString::can_cast(e.kind())
+                            })
                     }
+                    _ => {}
                 }
             }
 
@@ -198,15 +202,18 @@ pub(crate) fn highlight(
 
         let is_format_string = format_string.as_ref() == Some(&element_to_highlight);
 
-        if let Some((highlight, binding_hash)) =
-            highlight_element(&sema, &mut bindings_shadow_count, element_to_highlight.clone())
-        {
+        if let Some((highlight, binding_hash)) = highlight_element(
+            &sema,
+            &mut bindings_shadow_count,
+            syntactic_name_ref_highlighting,
+            element_to_highlight.clone(),
+        ) {
             stack.add(HighlightedRange { range, highlight, binding_hash });
             if let Some(string) =
                 element_to_highlight.as_token().cloned().and_then(ast::String::cast)
             {
-                stack.push();
                 if is_format_string {
+                    stack.push();
                     string.lex_format_specifier(|piece_range, kind| {
                         if let Some(highlight) = highlight_format_specifier(kind) {
                             stack.add(HighlightedRange {
@@ -216,13 +223,27 @@ pub(crate) fn highlight(
                             });
                         }
                     });
+                    stack.pop();
+                }
+                // Highlight escape sequences
+                if let Some(char_ranges) = string.char_ranges() {
+                    stack.push();
+                    for (piece_range, _) in char_ranges.iter().filter(|(_, char)| char.is_ok()) {
+                        if string.text()[piece_range.start().into()..].starts_with('\\') {
+                            stack.add(HighlightedRange {
+                                range: piece_range + range.start(),
+                                highlight: HighlightTag::EscapeSequence.into(),
+                                binding_hash: None,
+                            });
+                        }
+                    }
+                    stack.pop_and_inject(false);
                 }
-                stack.pop();
             } else if let Some(string) =
                 element_to_highlight.as_token().cloned().and_then(ast::RawString::cast)
             {
-                stack.push();
                 if is_format_string {
+                    stack.push();
                     string.lex_format_specifier(|piece_range, kind| {
                         if let Some(highlight) = highlight_format_specifier(kind) {
                             stack.add(HighlightedRange {
@@ -232,8 +253,8 @@ pub(crate) fn highlight(
                             });
                         }
                     });
+                    stack.pop();
                 }
-                stack.pop();
             }
         }
     }
@@ -408,6 +429,7 @@ fn macro_call_range(macro_call: &ast::MacroCall) -> Option<TextRange> {
 fn highlight_element(
     sema: &Semantics<RootDatabase>,
     bindings_shadow_count: &mut FxHashMap<Name, u32>,
+    syntactic_name_ref_highlighting: bool,
     element: SyntaxElement,
 ) -> Option<(Highlight, Option<u64>)> {
     let db = sema.db;
@@ -461,12 +483,20 @@ fn highlight_element(
                     }
                     NameRefClass::FieldShorthand { .. } => HighlightTag::Field.into(),
                 },
+                None if syntactic_name_ref_highlighting => highlight_name_ref_by_syntax(name_ref),
                 None => HighlightTag::UnresolvedReference.into(),
             }
         }
 
         // Simple token-based highlighting
-        COMMENT => HighlightTag::Comment.into(),
+        COMMENT => {
+            let comment = element.into_token().and_then(ast::Comment::cast)?;
+            let h = HighlightTag::Comment;
+            match comment.kind().doc {
+                Some(_) => h | HighlightModifier::Documentation,
+                None => h.into(),
+            }
+        }
         STRING | RAW_STRING | RAW_BYTE_STRING | BYTE_STRING => HighlightTag::StringLiteral.into(),
         ATTR => HighlightTag::Attribute.into(),
         INT_NUMBER | FLOAT_NUMBER => HighlightTag::NumericLiteral.into(),
@@ -493,6 +523,9 @@ fn highlight_element(
             h |= HighlightModifier::Unsafe;
             h
         }
+        T![!] if element.parent().and_then(ast::MacroCall::cast).is_some() => {
+            Highlight::new(HighlightTag::Macro)
+        }
 
         k if k.is_keyword() => {
             let h = Highlight::new(HighlightTag::Keyword);
@@ -609,3 +642,53 @@ fn highlight_name_by_syntax(name: ast::Name) -> Highlight {
 
     tag.into()
 }
+
+fn highlight_name_ref_by_syntax(name: ast::NameRef) -> Highlight {
+    let default = HighlightTag::UnresolvedReference;
+
+    let parent = match name.syntax().parent() {
+        Some(it) => it,
+        _ => return default.into(),
+    };
+
+    let tag = match parent.kind() {
+        METHOD_CALL_EXPR => HighlightTag::Function,
+        FIELD_EXPR => HighlightTag::Field,
+        PATH_SEGMENT => {
+            let path = match parent.parent().and_then(ast::Path::cast) {
+                Some(it) => it,
+                _ => return default.into(),
+            };
+            let expr = match path.syntax().parent().and_then(ast::PathExpr::cast) {
+                Some(it) => it,
+                _ => {
+                    // within path, decide whether it is module or adt by checking for uppercase name
+                    return if name.text().chars().next().unwrap_or_default().is_uppercase() {
+                        HighlightTag::Struct
+                    } else {
+                        HighlightTag::Module
+                    }
+                    .into();
+                }
+            };
+            let parent = match expr.syntax().parent() {
+                Some(it) => it,
+                None => return default.into(),
+            };
+
+            match parent.kind() {
+                CALL_EXPR => HighlightTag::Function,
+                _ => {
+                    if name.text().chars().next().unwrap_or_default().is_uppercase() {
+                        HighlightTag::Struct
+                    } else {
+                        HighlightTag::Constant
+                    }
+                }
+            }
+        }
+        _ => default,
+    };
+
+    tag.into()
+}
diff --git a/crates/ra_ide/src/syntax_highlighting/html.rs b/crates/ra_ide/src/syntax_highlighting/html.rs
index 5bada6252..99b6b25ab 100644
--- a/crates/ra_ide/src/syntax_highlighting/html.rs
+++ b/crates/ra_ide/src/syntax_highlighting/html.rs
@@ -19,7 +19,7 @@ pub(crate) fn highlight_as_html(db: &RootDatabase, file_id: FileId, rainbow: boo
         )
     }
 
-    let ranges = highlight(db, file_id, None);
+    let ranges = highlight(db, file_id, None, false);
     let text = parse.tree().syntax().to_string();
     let mut prev_pos = TextSize::from(0);
     let mut buf = String::new();
@@ -84,6 +84,8 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .variable           { color: #DCDCCC; }
 .format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
+.unresolved_reference { color: #FC5555; }
+.escape_sequence    { color: #94BFF3; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
 .keyword.unsafe     { color: #BC8383; font-weight: bold; }
diff --git a/crates/ra_ide/src/syntax_highlighting/injection.rs b/crates/ra_ide/src/syntax_highlighting/injection.rs
index 3575a0fc6..415f24a6d 100644
--- a/crates/ra_ide/src/syntax_highlighting/injection.rs
+++ b/crates/ra_ide/src/syntax_highlighting/injection.rs
@@ -7,7 +7,10 @@ use hir::Semantics;
 use ra_syntax::{ast, AstToken, SyntaxNode, SyntaxToken, TextRange, TextSize};
 use stdx::SepBy;
 
-use crate::{call_info::ActiveParameter, Analysis, HighlightTag, HighlightedRange, RootDatabase};
+use crate::{
+    call_info::ActiveParameter, Analysis, HighlightModifier, HighlightTag, HighlightedRange,
+    RootDatabase,
+};
 
 use super::HighlightedRangeStack;
 
@@ -53,6 +56,10 @@ pub(super) fn highlight_injection(
 /// Mapping from extracted documentation code to original code
 type RangesMap = BTreeMap<TextSize, TextSize>;
 
+const RUSTDOC_FENCE: &'static str = "```";
+const RUSTDOC_FENCE_TOKENS: &[&'static str] =
+    &["", "rust", "should_panic", "ignore", "no_run", "compile_fail", "edition2015", "edition2018"];
+
 /// Extracts Rust code from documentation comments as well as a mapping from
 /// the extracted source code back to the original source ranges.
 /// Lastly, a vector of new comment highlight ranges (spanning only the
@@ -67,6 +74,7 @@ pub(super) fn extract_doc_comments(
     // Mapping from extracted documentation code to original code
     let mut range_mapping: RangesMap = BTreeMap::new();
     let mut line_start = TextSize::try_from(prefix.len()).unwrap();
+    let mut is_codeblock = false;
     let mut is_doctest = false;
     // Replace the original, line-spanning comment ranges by new, only comment-prefix
     // spanning comment ranges.
@@ -76,8 +84,13 @@ pub(super) fn extract_doc_comments(
         .filter_map(|el| el.into_token().and_then(ast::Comment::cast))
         .filter(|comment| comment.kind().doc.is_some())
         .filter(|comment| {
-            if comment.text().contains("```") {
-                is_doctest = !is_doctest;
+            if let Some(idx) = comment.text().find(RUSTDOC_FENCE) {
+                is_codeblock = !is_codeblock;
+                // Check whether code is rust by inspecting fence guards
+                let guards = &comment.text()[idx + RUSTDOC_FENCE.len()..];
+                let is_rust =
+                    guards.split(',').all(|sub| RUSTDOC_FENCE_TOKENS.contains(&sub.trim()));
+                is_doctest = is_codeblock && is_rust;
                 false
             } else {
                 is_doctest
@@ -108,7 +121,7 @@ pub(super) fn extract_doc_comments(
                     range.start(),
                     range.start() + TextSize::try_from(pos).unwrap(),
                 ),
-                highlight: HighlightTag::Comment.into(),
+                highlight: HighlightTag::Comment | HighlightModifier::Documentation,
                 binding_hash: None,
             });
             line_start += range.len() - TextSize::try_from(pos).unwrap();
@@ -137,7 +150,7 @@ pub(super) fn highlight_doc_comment(
     let (analysis, tmp_file_id) = Analysis::from_single_file(text);
 
     stack.push();
-    for mut h in analysis.highlight(tmp_file_id).unwrap() {
+    for mut h in analysis.with_db(|db| super::highlight(db, tmp_file_id, None, true)).unwrap() {
         // Determine start offset and end offset in case of multi-line ranges
         let mut start_offset = None;
         let mut end_offset = None;
@@ -154,6 +167,7 @@ pub(super) fn highlight_doc_comment(
                 h.range.start() + start_offset,
                 h.range.end() + end_offset.unwrap_or(start_offset),
             );
+
             stack.add(h);
         }
     }
diff --git a/crates/ra_ide/src/syntax_highlighting/tags.rs b/crates/ra_ide/src/syntax_highlighting/tags.rs
index 94f466966..93bbb4b4d 100644
--- a/crates/ra_ide/src/syntax_highlighting/tags.rs
+++ b/crates/ra_ide/src/syntax_highlighting/tags.rs
@@ -23,6 +23,7 @@ pub enum HighlightTag {
     Constant,
     Enum,
     EnumVariant,
+    EscapeSequence,
     Field,
     FormatSpecifier,
     Function,
@@ -55,6 +56,7 @@ pub enum HighlightModifier {
     /// `foo` in `fn foo(x: i32)` is a definition, `foo` in `foo(90 + 2)` is
     /// not.
     Definition,
+    Documentation,
     Mutable,
     Unsafe,
 }
@@ -71,6 +73,7 @@ impl HighlightTag {
             HighlightTag::Constant => "constant",
             HighlightTag::Enum => "enum",
             HighlightTag::EnumVariant => "enum_variant",
+            HighlightTag::EscapeSequence => "escape_sequence",
             HighlightTag::Field => "field",
             HighlightTag::FormatSpecifier => "format_specifier",
             HighlightTag::Function => "function",
@@ -106,6 +109,7 @@ impl HighlightModifier {
         HighlightModifier::Attribute,
         HighlightModifier::ControlFlow,
         HighlightModifier::Definition,
+        HighlightModifier::Documentation,
         HighlightModifier::Mutable,
         HighlightModifier::Unsafe,
     ];
@@ -115,6 +119,7 @@ impl HighlightModifier {
             HighlightModifier::Attribute => "attribute",
             HighlightModifier::ControlFlow => "control",
             HighlightModifier::Definition => "declaration",
+            HighlightModifier::Documentation => "documentation",
             HighlightModifier::Mutable => "mutable",
             HighlightModifier::Unsafe => "unsafe",
         }
diff --git a/crates/ra_ide/src/syntax_highlighting/tests.rs b/crates/ra_ide/src/syntax_highlighting/tests.rs
index 949bf59a0..b4d56a7a0 100644
--- a/crates/ra_ide/src/syntax_highlighting/tests.rs
+++ b/crates/ra_ide/src/syntax_highlighting/tests.rs
@@ -43,6 +43,12 @@ def_fn! {
     }
 }
 
+macro_rules! noop {
+    ($expr:expr) => {
+        $expr
+    }
+}
+
 // comment
 fn main() {
     println!("Hello, {}!", 92);
@@ -61,6 +67,8 @@ fn main() {
         // Do nothing
     }
 
+    noop!(noop!(1));
+
     let mut x = 42;
     let y = &mut x;
     let z = &y;
@@ -238,6 +246,10 @@ fn main() {
 
     println!(r"Hello, {}!", "world");
 
+    // escape sequences
+    println!("Hello\nWorld");
+    println!("\u{48}\x65\x6C\x6C\x6F World");
+
     println!("{\x41}", A = 92);
     println!("{ничоси}", ничоси = 92);
 }"#
@@ -279,7 +291,13 @@ fn main() {
 fn test_highlight_doctest() {
     check_highlighting(
         r#"
+struct Foo {
+    bar: bool,
+}
+
 impl Foo {
+    pub const bar: bool = true;
+
     /// Constructs a new `Foo`.
     ///
     /// # Examples
@@ -289,7 +307,7 @@ impl Foo {
     /// let mut foo: Foo = Foo::new();
     /// ```
     pub const fn new() -> Foo {
-        Foo { }
+        Foo { bar: true }
     }
 
     /// `bar` method on `Foo`.
@@ -297,11 +315,15 @@ impl Foo {
     /// # Examples
     ///
     /// ```
+    /// use x::y;
+    ///
     /// let foo = Foo::new();
     ///
     /// // calls bar on foo
     /// assert!(foo.bar());
     ///
+    /// let bar = foo.bar || Foo::bar;
+    ///
     /// /* multi-line
     ///        comment */
     ///
@@ -311,9 +333,13 @@ impl Foo {
     ///
     /// ```
     ///
-    /// ```
+    /// ```rust,no_run
     /// let foobar = Foo::new().bar();
     /// ```
+    ///
+    /// ```sh
+    /// echo 1
+    /// ```
     pub fn foo(&self) -> bool {
         true
     }
@@ -322,7 +348,7 @@ impl Foo {
         .trim(),
         "crates/ra_ide/src/snapshots/highlight_doctest.html",
         false,
-    )
+    );
 }
 
 /// Highlights the code given by the `ra_fixture` argument, renders the
diff --git a/crates/ra_ide_db/src/change.rs b/crates/ra_ide_db/src/change.rs
index 2fc796a85..78ee6a515 100644
--- a/crates/ra_ide_db/src/change.rs
+++ b/crates/ra_ide_db/src/change.rs
@@ -9,22 +9,15 @@ use ra_db::{
     SourceRootId,
 };
 use ra_prof::{memory_usage, profile, Bytes};
-use ra_syntax::SourceFile;
-#[cfg(not(feature = "wasm"))]
-use rayon::prelude::*;
 use rustc_hash::FxHashMap;
 
-use crate::{
-    symbol_index::{SymbolIndex, SymbolsDatabase},
-    RootDatabase,
-};
+use crate::{symbol_index::SymbolsDatabase, RootDatabase};
 
 #[derive(Default)]
 pub struct AnalysisChange {
     new_roots: Vec<(SourceRootId, bool)>,
     roots_changed: FxHashMap<SourceRootId, RootChange>,
     files_changed: Vec<(FileId, Arc<String>)>,
-    libraries_added: Vec<LibraryData>,
     crate_graph: Option<CrateGraph>,
 }
 
@@ -40,9 +33,6 @@ impl fmt::Debug for AnalysisChange {
         if !self.files_changed.is_empty() {
             d.field("files_changed", &self.files_changed.len());
         }
-        if !self.libraries_added.is_empty() {
-            d.field("libraries_added", &self.libraries_added.len());
-        }
         if self.crate_graph.is_some() {
             d.field("crate_graph", &self.crate_graph);
         }
@@ -79,10 +69,6 @@ impl AnalysisChange {
         self.roots_changed.entry(root_id).or_default().removed.push(file);
     }
 
-    pub fn add_library(&mut self, data: LibraryData) {
-        self.libraries_added.push(data)
-    }
-
     pub fn set_crate_graph(&mut self, graph: CrateGraph) {
         self.crate_graph = Some(graph);
     }
@@ -116,47 +102,6 @@ impl fmt::Debug for RootChange {
     }
 }
 
-pub struct LibraryData {
-    root_id: SourceRootId,
-    root_change: RootChange,
-    symbol_index: SymbolIndex,
-}
-
-impl fmt::Debug for LibraryData {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.debug_struct("LibraryData")
-            .field("root_id", &self.root_id)
-            .field("root_change", &self.root_change)
-            .field("n_symbols", &self.symbol_index.len())
-            .finish()
-    }
-}
-
-impl LibraryData {
-    pub fn prepare(
-        root_id: SourceRootId,
-        files: Vec<(FileId, RelativePathBuf, Arc<String>)>,
-    ) -> LibraryData {
-        let _p = profile("LibraryData::prepare");
-
-        #[cfg(not(feature = "wasm"))]
-        let iter = files.par_iter();
-        #[cfg(feature = "wasm")]
-        let iter = files.iter();
-
-        let symbol_index = SymbolIndex::for_files(iter.map(|(file_id, _, text)| {
-            let parse = SourceFile::parse(text);
-            (*file_id, parse)
-        }));
-        let mut root_change = RootChange::default();
-        root_change.added = files
-            .into_iter()
-            .map(|(file_id, path, text)| AddFile { file_id, path, text })
-            .collect();
-        LibraryData { root_id, root_change, symbol_index }
-    }
-}
-
 const GC_COOLDOWN: time::Duration = time::Duration::from_millis(100);
 
 impl RootDatabase {
@@ -171,6 +116,7 @@ impl RootDatabase {
         log::info!("apply_change {:?}", change);
         if !change.new_roots.is_empty() {
             let mut local_roots = Vec::clone(&self.local_roots());
+            let mut libraries = Vec::clone(&self.library_roots());
             for (root_id, is_local) in change.new_roots {
                 let root =
                     if is_local { SourceRoot::new_local() } else { SourceRoot::new_library() };
@@ -178,9 +124,12 @@ impl RootDatabase {
                 self.set_source_root_with_durability(root_id, Arc::new(root), durability);
                 if is_local {
                     local_roots.push(root_id);
+                } else {
+                    libraries.push(root_id)
                 }
             }
             self.set_local_roots_with_durability(Arc::new(local_roots), Durability::HIGH);
+            self.set_library_roots_with_durability(Arc::new(libraries), Durability::HIGH);
         }
 
         for (root_id, root_change) in change.roots_changed {
@@ -192,24 +141,6 @@ impl RootDatabase {
             let durability = durability(&source_root);
             self.set_file_text_with_durability(file_id, text, durability)
         }
-        if !change.libraries_added.is_empty() {
-            let mut libraries = Vec::clone(&self.library_roots());
-            for library in change.libraries_added {
-                libraries.push(library.root_id);
-                self.set_source_root_with_durability(
-                    library.root_id,
-                    Arc::new(SourceRoot::new_library()),
-                    Durability::HIGH,
-                );
-                self.set_library_symbols_with_durability(
-                    library.root_id,
-                    Arc::new(library.symbol_index),
-                    Durability::HIGH,
-                );
-                self.apply_root_change(library.root_id, library.root_change);
-            }
-            self.set_library_roots_with_durability(Arc::new(libraries), Durability::HIGH);
-        }
         if let Some(crate_graph) = change.crate_graph {
             self.set_crate_graph_with_durability(Arc::new(crate_graph), Durability::HIGH)
         }
diff --git a/crates/ra_ide_db/src/source_change.rs b/crates/ra_ide_db/src/source_change.rs
index f40ae8304..0bbd3c3e5 100644
--- a/crates/ra_ide_db/src/source_change.rs
+++ b/crates/ra_ide_db/src/source_change.rs
@@ -3,7 +3,7 @@
 //!
 //! It can be viewed as a dual for `AnalysisChange`.
 
-use ra_db::{FileId, RelativePathBuf, SourceRootId};
+use ra_db::FileId;
 use ra_text_edit::TextEdit;
 
 #[derive(Debug, Clone)]
@@ -44,8 +44,8 @@ impl From<Vec<SourceFileEdit>> for SourceChange {
 
 #[derive(Debug, Clone)]
 pub enum FileSystemEdit {
-    CreateFile { source_root: SourceRootId, path: RelativePathBuf },
-    MoveFile { src: FileId, dst_source_root: SourceRootId, dst_path: RelativePathBuf },
+    CreateFile { anchor: FileId, dst: String },
+    MoveFile { src: FileId, anchor: FileId, dst: String },
 }
 
 impl From<FileSystemEdit> for SourceChange {
diff --git a/crates/ra_ide_db/src/symbol_index.rs b/crates/ra_ide_db/src/symbol_index.rs
index aab918973..25c99813f 100644
--- a/crates/ra_ide_db/src/symbol_index.rs
+++ b/crates/ra_ide_db/src/symbol_index.rs
@@ -34,14 +34,15 @@ use ra_db::{
     salsa::{self, ParallelDatabase},
     CrateId, FileId, SourceDatabaseExt, SourceRootId,
 };
+use ra_prof::profile;
 use ra_syntax::{
     ast::{self, NameOwner},
     match_ast, AstNode, Parse, SmolStr, SourceFile,
     SyntaxKind::{self, *},
     SyntaxNode, SyntaxNodePtr, TextRange, WalkEvent,
 };
-#[cfg(not(feature = "wasm"))]
 use rayon::prelude::*;
+use rustc_hash::FxHashMap;
 
 use crate::RootDatabase;
 
@@ -86,10 +87,9 @@ impl Query {
 }
 
 #[salsa::query_group(SymbolsDatabaseStorage)]
-pub trait SymbolsDatabase: hir::db::HirDatabase {
+pub trait SymbolsDatabase: hir::db::HirDatabase + SourceDatabaseExt + ParallelDatabase {
     fn file_symbols(&self, file_id: FileId) -> Arc<SymbolIndex>;
-    #[salsa::input]
-    fn library_symbols(&self, id: SourceRootId) -> Arc<SymbolIndex>;
+    fn library_symbols(&self) -> Arc<FxHashMap<SourceRootId, SymbolIndex>>;
     /// The set of "local" (that is, from the current workspace) roots.
     /// Files in local roots are assumed to change frequently.
     #[salsa::input]
@@ -100,6 +100,29 @@ pub trait SymbolsDatabase: hir::db::HirDatabase {
     fn library_roots(&self) -> Arc<Vec<SourceRootId>>;
 }
 
+fn library_symbols(
+    db: &(impl SymbolsDatabase + ParallelDatabase),
+) -> Arc<FxHashMap<SourceRootId, SymbolIndex>> {
+    let _p = profile("library_symbols");
+
+    let roots = db.library_roots();
+    let res = roots
+        .iter()
+        .map(|&root_id| {
+            let root = db.source_root(root_id);
+            let files = root
+                .walk()
+                .map(|it| (it, SourceDatabaseExt::file_text(db, it)))
+                .collect::<Vec<_>>();
+            let symbol_index = SymbolIndex::for_files(
+                files.into_par_iter().map(|(file, text)| (file, SourceFile::parse(&text))),
+            );
+            (root_id, symbol_index)
+        })
+        .collect();
+    Arc::new(res)
+}
+
 fn file_symbols(db: &impl SymbolsDatabase, file_id: FileId) -> Arc<SymbolIndex> {
     db.check_canceled();
     let parse = db.parse(file_id);
@@ -112,9 +135,9 @@ fn file_symbols(db: &impl SymbolsDatabase, file_id: FileId) -> Arc<SymbolIndex>
 }
 
 /// Need to wrap Snapshot to provide `Clone` impl for `map_with`
-struct Snap(salsa::Snapshot<RootDatabase>);
-impl Clone for Snap {
-    fn clone(&self) -> Snap {
+struct Snap<DB>(DB);
+impl<DB: ParallelDatabase> Clone for Snap<salsa::Snapshot<DB>> {
+    fn clone(&self) -> Snap<salsa::Snapshot<DB>> {
         Snap(self.0.snapshot())
     }
 }
@@ -143,19 +166,11 @@ impl Clone for Snap {
 pub fn world_symbols(db: &RootDatabase, query: Query) -> Vec<FileSymbol> {
     let _p = ra_prof::profile("world_symbols").detail(|| query.query.clone());
 
-    let buf: Vec<Arc<SymbolIndex>> = if query.libs {
-        let snap = Snap(db.snapshot());
-        #[cfg(not(feature = "wasm"))]
-        let buf = db
-            .library_roots()
-            .par_iter()
-            .map_with(snap, |db, &lib_id| db.0.library_symbols(lib_id))
-            .collect();
-
-        #[cfg(feature = "wasm")]
-        let buf = db.library_roots().iter().map(|&lib_id| snap.0.library_symbols(lib_id)).collect();
-
-        buf
+    let tmp1;
+    let tmp2;
+    let buf: Vec<&SymbolIndex> = if query.libs {
+        tmp1 = db.library_symbols();
+        tmp1.values().collect()
     } else {
         let mut files = Vec::new();
         for &root in db.local_roots().iter() {
@@ -164,14 +179,11 @@ pub fn world_symbols(db: &RootDatabase, query: Query) -> Vec<FileSymbol> {
         }
 
         let snap = Snap(db.snapshot());
-        #[cfg(not(feature = "wasm"))]
-        let buf =
-            files.par_iter().map_with(snap, |db, &file_id| db.0.file_symbols(file_id)).collect();
-
-        #[cfg(feature = "wasm")]
-        let buf = files.iter().map(|&file_id| snap.0.file_symbols(file_id)).collect();
-
-        buf
+        tmp2 = files
+            .par_iter()
+            .map_with(snap, |db, &file_id| db.0.file_symbols(file_id))
+            .collect::<Vec<_>>();
+        tmp2.iter().map(|it| &**it).collect()
     };
     query.search(&buf)
 }
@@ -191,14 +203,11 @@ pub fn crate_symbols(db: &RootDatabase, krate: CrateId, query: Query) -> Vec<Fil
 
     let snap = Snap(db.snapshot());
 
-    #[cfg(not(feature = "wasm"))]
     let buf = files
         .par_iter()
         .map_with(snap, |db, &file_id| db.0.file_symbols(file_id))
         .collect::<Vec<_>>();
-
-    #[cfg(feature = "wasm")]
-    let buf = files.iter().map(|&file_id| snap.0.file_symbols(file_id)).collect::<Vec<_>>();
+    let buf = buf.iter().map(|it| &**it).collect::<Vec<_>>();
 
     query.search(&buf)
 }
@@ -245,12 +254,8 @@ impl SymbolIndex {
             lhs_chars.cmp(rhs_chars)
         }
 
-        #[cfg(not(feature = "wasm"))]
         symbols.par_sort_by(cmp);
 
-        #[cfg(feature = "wasm")]
-        symbols.sort_by(cmp);
-
         let mut builder = fst::MapBuilder::memory();
 
         let mut last_batch_start = 0;
@@ -284,7 +289,6 @@ impl SymbolIndex {
         self.map.as_fst().size() + self.symbols.len() * mem::size_of::<FileSymbol>()
     }
 
-    #[cfg(not(feature = "wasm"))]
     pub(crate) fn for_files(
         files: impl ParallelIterator<Item = (FileId, Parse<ast::SourceFile>)>,
     ) -> SymbolIndex {
@@ -294,16 +298,6 @@ impl SymbolIndex {
         SymbolIndex::new(symbols)
     }
 
-    #[cfg(feature = "wasm")]
-    pub(crate) fn for_files(
-        files: impl Iterator<Item = (FileId, Parse<ast::SourceFile>)>,
-    ) -> SymbolIndex {
-        let symbols = files
-            .flat_map(|(file_id, file)| source_file_to_file_symbols(&file.tree(), file_id))
-            .collect::<Vec<_>>();
-        SymbolIndex::new(symbols)
-    }
-
     fn range_to_map_value(start: usize, end: usize) -> u64 {
         debug_assert![start <= (std::u32::MAX as usize)];
         debug_assert![end <= (std::u32::MAX as usize)];
@@ -319,7 +313,7 @@ impl SymbolIndex {
 }
 
 impl Query {
-    pub(crate) fn search(self, indices: &[Arc<SymbolIndex>]) -> Vec<FileSymbol> {
+    pub(crate) fn search(self, indices: &[&SymbolIndex]) -> Vec<FileSymbol> {
         let mut op = fst::map::OpBuilder::new();
         for file_symbols in indices.iter() {
             let automaton = fst::automaton::Subsequence::new(&self.lowercased);
diff --git a/crates/ra_parser/src/grammar/expressions.rs b/crates/ra_parser/src/grammar/expressions.rs
index d6e8df32a..6e72eea66 100644
--- a/crates/ra_parser/src/grammar/expressions.rs
+++ b/crates/ra_parser/src/grammar/expressions.rs
@@ -50,10 +50,8 @@ fn expr_no_struct(p: &mut Parser) {
 }
 
 fn is_expr_stmt_attr_allowed(kind: SyntaxKind) -> bool {
-    match kind {
-        BIN_EXPR | RANGE_EXPR | IF_EXPR => false,
-        _ => true,
-    }
+    let forbid = matches!(kind, BIN_EXPR | RANGE_EXPR);
+    !forbid
 }
 
 pub(super) fn stmt(p: &mut Parser, with_semi: StmtWithSemi) {
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index cb0e27dce..9541362f5 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -29,13 +29,7 @@ pub enum ProjectWorkspace {
     /// Project workspace was discovered by running `cargo metadata` and `rustc --print sysroot`.
     Cargo { cargo: CargoWorkspace, sysroot: Sysroot },
     /// Project workspace was manually specified using a `rust-project.json` file.
-    Json { project: JsonProject },
-}
-
-impl From<JsonProject> for ProjectWorkspace {
-    fn from(project: JsonProject) -> ProjectWorkspace {
-        ProjectWorkspace::Json { project }
-    }
+    Json { project: JsonProject, project_location: PathBuf },
 }
 
 /// `PackageRoot` describes a package root folder.
@@ -164,10 +158,15 @@ impl ProjectWorkspace {
                     format!("Failed to open json file {}", project_json.display())
                 })?;
                 let reader = BufReader::new(file);
+                let project_location = match project_json.parent() {
+                    Some(parent) => PathBuf::from(parent),
+                    None => PathBuf::new(),
+                };
                 ProjectWorkspace::Json {
                     project: from_reader(reader).with_context(|| {
                         format!("Failed to deserialize json file {}", project_json.display())
                     })?,
+                    project_location: project_location,
                 }
             }
             ProjectManifest::CargoToml(cargo_toml) => {
@@ -200,9 +199,11 @@ impl ProjectWorkspace {
     /// the root is a member of the current workspace
     pub fn to_roots(&self) -> Vec<PackageRoot> {
         match self {
-            ProjectWorkspace::Json { project } => {
-                project.roots.iter().map(|r| PackageRoot::new_member(r.path.clone())).collect()
-            }
+            ProjectWorkspace::Json { project, project_location } => project
+                .roots
+                .iter()
+                .map(|r| PackageRoot::new_member(project_location.join(&r.path)))
+                .collect(),
             ProjectWorkspace::Cargo { cargo, sysroot } => cargo
                 .packages()
                 .map(|pkg| PackageRoot {
@@ -219,7 +220,7 @@ impl ProjectWorkspace {
 
     pub fn proc_macro_dylib_paths(&self) -> Vec<PathBuf> {
         match self {
-            ProjectWorkspace::Json { project } => project
+            ProjectWorkspace::Json { project, .. } => project
                 .crates
                 .iter()
                 .filter_map(|krate| krate.proc_macro_dylib_path.as_ref())
@@ -235,7 +236,7 @@ impl ProjectWorkspace {
 
     pub fn n_packages(&self) -> usize {
         match self {
-            ProjectWorkspace::Json { project } => project.crates.len(),
+            ProjectWorkspace::Json { project, .. } => project.crates.len(),
             ProjectWorkspace::Cargo { cargo, sysroot } => {
                 cargo.packages().len() + sysroot.crates().len()
             }
@@ -251,13 +252,14 @@ impl ProjectWorkspace {
     ) -> CrateGraph {
         let mut crate_graph = CrateGraph::default();
         match self {
-            ProjectWorkspace::Json { project } => {
+            ProjectWorkspace::Json { project, project_location } => {
                 let crates: FxHashMap<_, _> = project
                     .crates
                     .iter()
                     .enumerate()
                     .filter_map(|(seq_index, krate)| {
-                        let file_id = load(&krate.root_module)?;
+                        let file_path = project_location.join(&krate.root_module);
+                        let file_id = load(&file_path)?;
                         let edition = match krate.edition {
                             json_project::Edition::Edition2015 => Edition::Edition2015,
                             json_project::Edition::Edition2018 => Edition::Edition2018,
@@ -540,7 +542,7 @@ impl ProjectWorkspace {
             ProjectWorkspace::Cargo { cargo, .. } => {
                 Some(cargo.workspace_root()).filter(|root| path.starts_with(root))
             }
-            ProjectWorkspace::Json { project: JsonProject { roots, .. } } => roots
+            ProjectWorkspace::Json { project: JsonProject { roots, .. }, .. } => roots
                 .iter()
                 .find(|root| path.starts_with(&root.path))
                 .map(|root| root.path.as_ref()),
diff --git a/crates/ra_syntax/src/algo.rs b/crates/ra_syntax/src/algo.rs
index 664894d1f..f7a885eb3 100644
--- a/crates/ra_syntax/src/algo.rs
+++ b/crates/ra_syntax/src/algo.rs
@@ -290,6 +290,11 @@ impl<'a> SyntaxRewriter<'a> {
         N::cast(self.rewrite(node.syntax())).unwrap()
     }
 
+    /// Returns a node that encompasses all replacements to be done by this rewriter.
+    ///
+    /// Passing the returned node to `rewrite` will apply all replacements queued up in `self`.
+    ///
+    /// Returns `None` when there are no replacements.
     pub fn rewrite_root(&self) -> Option<SyntaxNode> {
         assert!(self.f.is_none());
         self.replacements
@@ -298,6 +303,9 @@ impl<'a> SyntaxRewriter<'a> {
                 SyntaxElement::Node(it) => it.clone(),
                 SyntaxElement::Token(it) => it.parent(),
             })
+            // If we only have one replacement, we must return its parent node, since `rewrite` does
+            // not replace the node passed to it.
+            .map(|it| it.parent().unwrap_or(it))
             .fold1(|a, b| least_common_ancestor(&a, &b).unwrap())
     }
 
diff --git a/crates/ra_syntax/src/lib.rs b/crates/ra_syntax/src/lib.rs
index 61e686da5..a33a35cc1 100644
--- a/crates/ra_syntax/src/lib.rs
+++ b/crates/ra_syntax/src/lib.rs
@@ -51,7 +51,8 @@ pub use crate::{
     ptr::{AstPtr, SyntaxNodePtr},
     syntax_error::SyntaxError,
     syntax_node::{
-        Direction, NodeOrToken, SyntaxElement, SyntaxNode, SyntaxToken, SyntaxTreeBuilder,
+        Direction, NodeOrToken, SyntaxElement, SyntaxElementChildren, SyntaxNode,
+        SyntaxNodeChildren, SyntaxToken, SyntaxTreeBuilder,
     },
 };
 pub use ra_parser::{SyntaxKind, T};
diff --git a/crates/ra_syntax/src/parsing/text_token_source.rs b/crates/ra_syntax/src/parsing/text_token_source.rs
index 7ddc2c2c3..97aa3e795 100644
--- a/crates/ra_syntax/src/parsing/text_token_source.rs
+++ b/crates/ra_syntax/src/parsing/text_token_source.rs
@@ -1,40 +1,35 @@
-//! FIXME: write short doc here
+//! See `TextTokenSource` docs.
 
-use ra_parser::Token as PToken;
 use ra_parser::TokenSource;
 
 use crate::{parsing::lexer::Token, SyntaxKind::EOF, TextRange, TextSize};
 
+/// Implementation of `ra_parser::TokenSource` that takes tokens from source code text.
 pub(crate) struct TextTokenSource<'t> {
     text: &'t str,
-    /// start position of each token(expect whitespace and comment)
+    /// token and its start position (non-whitespace/comment tokens)
     /// ```non-rust
     ///  struct Foo;
-    /// ^------^---
-    /// |      |  ^-
-    /// 0      7  10
+    ///  ^------^--^-
+    ///  |      |    \________
+    ///  |      \____         \
+    ///  |           \         |
+    ///  (struct, 0) (Foo, 7) (;, 10)
     /// ```
-    /// (token, start_offset): `[(struct, 0), (Foo, 7), (;, 10)]`
-    start_offsets: Vec<TextSize>,
-    /// non-whitespace/comment tokens
-    /// ```non-rust
-    /// struct Foo {}
-    /// ^^^^^^ ^^^ ^^
-    /// ```
-    /// tokens: `[struct, Foo, {, }]`
-    tokens: Vec<Token>,
+    /// `[(struct, 0), (Foo, 7), (;, 10)]`
+    token_offset_pairs: Vec<(Token, TextSize)>,
 
     /// Current token and position
-    curr: (PToken, usize),
+    curr: (ra_parser::Token, usize),
 }
 
 impl<'t> TokenSource for TextTokenSource<'t> {
-    fn current(&self) -> PToken {
+    fn current(&self) -> ra_parser::Token {
         self.curr.0
     }
 
-    fn lookahead_nth(&self, n: usize) -> PToken {
-        mk_token(self.curr.1 + n, &self.start_offsets, &self.tokens)
+    fn lookahead_nth(&self, n: usize) -> ra_parser::Token {
+        mk_token(self.curr.1 + n, &self.token_offset_pairs)
     }
 
     fn bump(&mut self) {
@@ -43,45 +38,47 @@ impl<'t> TokenSource for TextTokenSource<'t> {
         }
 
         let pos = self.curr.1 + 1;
-        self.curr = (mk_token(pos, &self.start_offsets, &self.tokens), pos);
+        self.curr = (mk_token(pos, &self.token_offset_pairs), pos);
     }
 
     fn is_keyword(&self, kw: &str) -> bool {
-        let pos = self.curr.1;
-        if pos >= self.tokens.len() {
-            return false;
-        }
-        let range = TextRange::at(self.start_offsets[pos], self.tokens[pos].len);
-        self.text[range] == *kw
+        self.token_offset_pairs
+            .get(self.curr.1)
+            .map(|(token, offset)| &self.text[TextRange::at(*offset, token.len)] == kw)
+            .unwrap_or(false)
     }
 }
 
-fn mk_token(pos: usize, start_offsets: &[TextSize], tokens: &[Token]) -> PToken {
-    let kind = tokens.get(pos).map(|t| t.kind).unwrap_or(EOF);
-    let is_jointed_to_next = if pos + 1 < start_offsets.len() {
-        start_offsets[pos] + tokens[pos].len == start_offsets[pos + 1]
-    } else {
-        false
+fn mk_token(pos: usize, token_offset_pairs: &[(Token, TextSize)]) -> ra_parser::Token {
+    let (kind, is_jointed_to_next) = match token_offset_pairs.get(pos) {
+        Some((token, offset)) => (
+            token.kind,
+            token_offset_pairs
+                .get(pos + 1)
+                .map(|(_, next_offset)| offset + token.len == *next_offset)
+                .unwrap_or(false),
+        ),
+        None => (EOF, false),
     };
-
-    PToken { kind, is_jointed_to_next }
+    ra_parser::Token { kind, is_jointed_to_next }
 }
 
 impl<'t> TextTokenSource<'t> {
     /// Generate input from tokens(expect comment and whitespace).
     pub fn new(text: &'t str, raw_tokens: &'t [Token]) -> TextTokenSource<'t> {
-        let mut tokens = Vec::new();
-        let mut start_offsets = Vec::new();
-        let mut len = 0.into();
-        for &token in raw_tokens.iter() {
-            if !token.kind.is_trivia() {
-                tokens.push(token);
-                start_offsets.push(len);
-            }
-            len += token.len;
-        }
+        let token_offset_pairs: Vec<_> = raw_tokens
+            .iter()
+            .filter_map({
+                let mut len = 0.into();
+                move |token| {
+                    let pair = if token.kind.is_trivia() { None } else { Some((*token, len)) };
+                    len += token.len;
+                    pair
+                }
+            })
+            .collect();
 
-        let first = mk_token(0, &start_offsets, &tokens);
-        TextTokenSource { text, start_offsets, tokens, curr: (first, 0) }
+        let first = mk_token(0, &token_offset_pairs);
+        TextTokenSource { text, token_offset_pairs, curr: (first, 0) }
     }
 }
diff --git a/crates/ra_syntax/test_data/parser/inline/err/0009_attr_on_expr_not_allowed.rast b/crates/ra_syntax/test_data/parser/inline/err/0009_attr_on_expr_not_allowed.rast
index 0656fdf73..4e3fa704e 100644
--- a/crates/ra_syntax/test_data/parser/inline/err/0009_attr_on_expr_not_allowed.rast
+++ b/crates/ra_syntax/test_data/parser/inline/err/0009_attr_on_expr_not_allowed.rast
@@ -56,4 +56,3 @@ [email protected]
       [email protected] "}"
   [email protected] "\n"
 error 24..24: attributes are not allowed on BIN_EXPR
-error 44..44: attributes are not allowed on IF_EXPR
diff --git a/crates/rust-analyzer/build.rs b/crates/rust-analyzer/build.rs
index d4b010c04..5ae76ba30 100644
--- a/crates/rust-analyzer/build.rs
+++ b/crates/rust-analyzer/build.rs
@@ -5,11 +5,14 @@ use std::{env, path::PathBuf, process::Command};
 fn main() {
     set_rerun();
 
-    let rev = rev().unwrap_or_else(|| "???????".to_string());
+    let rev =
+        env::var("RUST_ANALYZER_REV").ok().or_else(rev).unwrap_or_else(|| "???????".to_string());
     println!("cargo:rustc-env=REV={}", rev)
 }
 
 fn set_rerun() {
+    println!("cargo:rerun-if-env-changed=RUST_ANALYZER_REV");
+
     let mut manifest_dir = PathBuf::from(
         env::var("CARGO_MANIFEST_DIR").expect("`CARGO_MANIFEST_DIR` is always set by cargo."),
     );
diff --git a/crates/rust-analyzer/src/bin/main.rs b/crates/rust-analyzer/src/bin/main.rs
index 8d071ab1c..99e3f7173 100644
--- a/crates/rust-analyzer/src/bin/main.rs
+++ b/crates/rust-analyzer/src/bin/main.rs
@@ -108,11 +108,11 @@ fn run_server() -> Result<()> {
             config.update(value);
         }
         config.update_caps(&initialize_params.capabilities);
+        let cwd = std::env::current_dir()?;
+        config.root_path =
+            initialize_params.root_uri.and_then(|it| it.to_file_path().ok()).unwrap_or(cwd);
 
         if config.linked_projects.is_empty() {
-            let cwd = std::env::current_dir()?;
-            let root =
-                initialize_params.root_uri.and_then(|it| it.to_file_path().ok()).unwrap_or(cwd);
             let workspace_roots = initialize_params
                 .workspace_folders
                 .map(|workspaces| {
@@ -122,7 +122,7 @@ fn run_server() -> Result<()> {
                         .collect::<Vec<_>>()
                 })
                 .filter(|workspaces| !workspaces.is_empty())
-                .unwrap_or_else(|| vec![root]);
+                .unwrap_or_else(|| vec![config.root_path.clone()]);
 
             config.linked_projects = ProjectManifest::discover_all(&workspace_roots)
                 .into_iter()
diff --git a/crates/rust-analyzer/src/cargo_target_spec.rs b/crates/rust-analyzer/src/cargo_target_spec.rs
index 44f856f6b..5c22dce0d 100644
--- a/crates/rust-analyzer/src/cargo_target_spec.rs
+++ b/crates/rust-analyzer/src/cargo_target_spec.rs
@@ -2,7 +2,7 @@
 
 use ra_cfg::CfgExpr;
 use ra_ide::{FileId, RunnableKind, TestId};
-use ra_project_model::{self, ProjectWorkspace, TargetKind};
+use ra_project_model::{self, TargetKind};
 
 use crate::{global_state::GlobalStateSnapshot, Result};
 
@@ -89,27 +89,23 @@ impl CargoTargetSpec {
     }
 
     pub(crate) fn for_file(
-        world: &GlobalStateSnapshot,
+        global_state_snapshot: &GlobalStateSnapshot,
         file_id: FileId,
     ) -> Result<Option<CargoTargetSpec>> {
-        let &crate_id = match world.analysis().crate_for(file_id)?.first() {
-            Some(crate_id) => crate_id,
+        let crate_id = match global_state_snapshot.analysis().crate_for(file_id)?.first() {
+            Some(crate_id) => *crate_id,
             None => return Ok(None),
         };
-        let file_id = world.analysis().crate_root(crate_id)?;
-        let path = world.file_id_to_path(file_id);
-        let res = world.workspaces.iter().find_map(|ws| match ws {
-            ProjectWorkspace::Cargo { cargo, .. } => {
-                let tgt = cargo.target_by_root(&path)?;
-                Some(CargoTargetSpec {
-                    package: cargo.package_flag(&cargo[cargo[tgt].package]),
-                    target: cargo[tgt].name.clone(),
-                    target_kind: cargo[tgt].kind,
-                })
-            }
-            ProjectWorkspace::Json { .. } => None,
-        });
-        Ok(res)
+        let (cargo_ws, target) = match global_state_snapshot.cargo_target_for_crate_root(crate_id) {
+            Some(it) => it,
+            None => return Ok(None),
+        };
+        let res = CargoTargetSpec {
+            package: cargo_ws.package_flag(&cargo_ws[cargo_ws[target].package]),
+            target: cargo_ws[target].name.clone(),
+            target_kind: cargo_ws[target].kind,
+        };
+        Ok(Some(res))
     }
 
     pub(crate) fn push_to(self, buf: &mut Vec<String>, kind: &RunnableKind) {
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 1253db836..aa2c4ae15 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -9,6 +9,7 @@
 
 use std::{ffi::OsString, path::PathBuf};
 
+use crate::diagnostics::DiagnosticsConfig;
 use lsp_types::ClientCapabilities;
 use ra_flycheck::FlycheckConfig;
 use ra_ide::{AssistConfig, CompletionConfig, HoverConfig, InlayHintsConfig};
@@ -20,6 +21,7 @@ pub struct Config {
     pub client_caps: ClientCapsConfig,
 
     pub publish_diagnostics: bool,
+    pub diagnostics: DiagnosticsConfig,
     pub lru_capacity: Option<usize>,
     pub proc_macro_srv: Option<(PathBuf, Vec<OsString>)>,
     pub files: FilesConfig,
@@ -38,12 +40,13 @@ pub struct Config {
 
     pub with_sysroot: bool,
     pub linked_projects: Vec<LinkedProject>,
+    pub root_path: PathBuf,
 }
 
 #[derive(Debug, Clone)]
 pub enum LinkedProject {
     ProjectManifest(ProjectManifest),
-    JsonProject(JsonProject),
+    InlineJsonProject(JsonProject),
 }
 
 impl From<ProjectManifest> for LinkedProject {
@@ -54,7 +57,7 @@ impl From<ProjectManifest> for LinkedProject {
 
 impl From<JsonProject> for LinkedProject {
     fn from(v: JsonProject) -> Self {
-        LinkedProject::JsonProject(v)
+        LinkedProject::InlineJsonProject(v)
     }
 }
 
@@ -135,6 +138,7 @@ impl Default for Config {
 
             with_sysroot: true,
             publish_diagnostics: true,
+            diagnostics: DiagnosticsConfig::default(),
             lru_capacity: None,
             proc_macro_srv: None,
             files: FilesConfig { watcher: FilesWatcher::Notify, exclude: Vec::new() },
@@ -167,6 +171,7 @@ impl Default for Config {
             lens: LensConfig::default(),
             hover: HoverConfig::default(),
             linked_projects: Vec::new(),
+            root_path: PathBuf::new(),
         }
     }
 }
@@ -182,6 +187,8 @@ impl Config {
 
         set(value, "/withSysroot", &mut self.with_sysroot);
         set(value, "/diagnostics/enable", &mut self.publish_diagnostics);
+        set(value, "/diagnostics/warningsAsInfo", &mut self.diagnostics.warnings_as_info);
+        set(value, "/diagnostics/warningsAsHint", &mut self.diagnostics.warnings_as_hint);
         set(value, "/lruCapacity", &mut self.lru_capacity);
         self.files.watcher = match get(value, "/files/watcher") {
             Some("client") => FilesWatcher::Client,
@@ -289,6 +296,7 @@ impl Config {
             set(value, "/hoverActions/implementations", &mut self.hover.implementations);
             set(value, "/hoverActions/run", &mut self.hover.run);
             set(value, "/hoverActions/debug", &mut self.hover.debug);
+            set(value, "/hoverActions/gotoTypeDef", &mut self.hover.goto_type_def);
         } else {
             self.hover = HoverConfig::NO_ACTIONS;
         }
diff --git a/crates/rust-analyzer/src/diagnostics.rs b/crates/rust-analyzer/src/diagnostics.rs
index 25856c543..290609e7f 100644
--- a/crates/rust-analyzer/src/diagnostics.rs
+++ b/crates/rust-analyzer/src/diagnostics.rs
@@ -11,6 +11,12 @@ use crate::lsp_ext;
 pub type CheckFixes = Arc<HashMap<FileId, Vec<Fix>>>;
 
 #[derive(Debug, Default, Clone)]
+pub struct DiagnosticsConfig {
+    pub warnings_as_info: Vec<String>,
+    pub warnings_as_hint: Vec<String>,
+}
+
+#[derive(Debug, Default, Clone)]
 pub struct DiagnosticCollection {
     pub native: HashMap<FileId, Vec<Diagnostic>>,
     pub check: HashMap<FileId, Vec<Diagnostic>>,
diff --git a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
index f0273315e..9a7972ff5 100644
--- a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
@@ -29,7 +29,7 @@ expression: diag
                 },
             },
             severity: Some(
-                Hint,
+                Warning,
             ),
             code: Some(
                 String(
diff --git a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable_as_hint.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable_as_hint.snap
new file mode 100644
index 000000000..f0273315e
--- /dev/null
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable_as_hint.snap
@@ -0,0 +1,86 @@
+---
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
+expression: diag
+---
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/driver/subcommand/repl.rs",
+            range: Range {
+                start: Position {
+                    line: 290,
+                    character: 8,
+                },
+                end: Position {
+                    line: 290,
+                    character: 11,
+                },
+            },
+        },
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 290,
+                    character: 8,
+                },
+                end: Position {
+                    line: 290,
+                    character: 11,
+                },
+            },
+            severity: Some(
+                Hint,
+            ),
+            code: Some(
+                String(
+                    "unused_variables",
+                ),
+            ),
+            source: Some(
+                "rustc",
+            ),
+            message: "unused variable: `foo`\n#[warn(unused_variables)] on by default",
+            related_information: None,
+            tags: Some(
+                [
+                    Unnecessary,
+                ],
+            ),
+        },
+        fixes: [
+            CodeAction {
+                title: "consider prefixing with an underscore",
+                id: None,
+                group: None,
+                kind: Some(
+                    "quickfix",
+                ),
+                command: None,
+                edit: Some(
+                    SnippetWorkspaceEdit {
+                        changes: Some(
+                            {
+                                "file:///test/driver/subcommand/repl.rs": [
+                                    TextEdit {
+                                        range: Range {
+                                            start: Position {
+                                                line: 290,
+                                                character: 8,
+                                            },
+                                            end: Position {
+                                                line: 290,
+                                                character: 11,
+                                            },
+                                        },
+                                        new_text: "_foo",
+                                    },
+                                ],
+                            },
+                        ),
+                        document_changes: None,
+                    },
+                ),
+            },
+        ],
+    },
+]
diff --git a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable_as_info.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable_as_info.snap
new file mode 100644
index 000000000..85fd050fd
--- /dev/null
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable_as_info.snap
@@ -0,0 +1,86 @@
+---
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
+expression: diag
+---
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/driver/subcommand/repl.rs",
+            range: Range {
+                start: Position {
+                    line: 290,
+                    character: 8,
+                },
+                end: Position {
+                    line: 290,
+                    character: 11,
+                },
+            },
+        },
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 290,
+                    character: 8,
+                },
+                end: Position {
+                    line: 290,
+                    character: 11,
+                },
+            },
+            severity: Some(
+                Information,
+            ),
+            code: Some(
+                String(
+                    "unused_variables",
+                ),
+            ),
+            source: Some(
+                "rustc",
+            ),
+            message: "unused variable: `foo`\n#[warn(unused_variables)] on by default",
+            related_information: None,
+            tags: Some(
+                [
+                    Unnecessary,
+                ],
+            ),
+        },
+        fixes: [
+            CodeAction {
+                title: "consider prefixing with an underscore",
+                id: None,
+                group: None,
+                kind: Some(
+                    "quickfix",
+                ),
+                command: None,
+                edit: Some(
+                    SnippetWorkspaceEdit {
+                        changes: Some(
+                            {
+                                "file:///test/driver/subcommand/repl.rs": [
+                                    TextEdit {
+                                        range: Range {
+                                            start: Position {
+                                                line: 290,
+                                                character: 8,
+                                            },
+                                            end: Position {
+                                                line: 290,
+                                                character: 11,
+                                            },
+                                        },
+                                        new_text: "_foo",
+                                    },
+                                ],
+                            },
+                        ),
+                        document_changes: None,
+                    },
+                ),
+            },
+        ],
+    },
+]
diff --git a/crates/rust-analyzer/src/diagnostics/to_proto.rs b/crates/rust-analyzer/src/diagnostics/to_proto.rs
index 04e286780..ba74f15f3 100644
--- a/crates/rust-analyzer/src/diagnostics/to_proto.rs
+++ b/crates/rust-analyzer/src/diagnostics/to_proto.rs
@@ -1,10 +1,6 @@
 //! This module provides the functionality needed to convert diagnostics from
 //! `cargo check` json format to the LSP diagnostic format.
-use std::{
-    collections::HashMap,
-    path::{Component, Path, Prefix},
-    str::FromStr,
-};
+use std::{collections::HashMap, path::Path};
 
 use lsp_types::{
     Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag, Location,
@@ -13,14 +9,24 @@ use lsp_types::{
 use ra_flycheck::{Applicability, DiagnosticLevel, DiagnosticSpan, DiagnosticSpanMacroExpansion};
 use stdx::format_to;
 
-use crate::{lsp_ext, Result};
+use super::DiagnosticsConfig;
+use crate::{lsp_ext, to_proto::url_from_abs_path};
 
-/// Converts a Rust level string to a LSP severity
-fn map_level_to_severity(val: DiagnosticLevel) -> Option<DiagnosticSeverity> {
-    let res = match val {
+/// Determines the LSP severity from a diagnostic
+fn map_diagnostic_to_severity(
+    config: &DiagnosticsConfig,
+    val: &ra_flycheck::Diagnostic,
+) -> Option<DiagnosticSeverity> {
+    let res = match val.level {
         DiagnosticLevel::Ice => DiagnosticSeverity::Error,
         DiagnosticLevel::Error => DiagnosticSeverity::Error,
-        DiagnosticLevel::Warning => DiagnosticSeverity::Warning,
+        DiagnosticLevel::Warning => match &val.code {
+            Some(code) if config.warnings_as_hint.contains(&code.code) => DiagnosticSeverity::Hint,
+            Some(code) if config.warnings_as_info.contains(&code.code) => {
+                DiagnosticSeverity::Information
+            }
+            _ => DiagnosticSeverity::Warning,
+        },
         DiagnosticLevel::Note => DiagnosticSeverity::Information,
         DiagnosticLevel::Help => DiagnosticSeverity::Hint,
         DiagnosticLevel::Unknown => return None,
@@ -65,7 +71,7 @@ fn map_span_to_location(span: &DiagnosticSpan, workspace_root: &Path) -> Locatio
 fn map_span_to_location_naive(span: &DiagnosticSpan, workspace_root: &Path) -> Location {
     let mut file_name = workspace_root.to_path_buf();
     file_name.push(&span.file_name);
-    let uri = url_from_path_with_drive_lowercasing(file_name).unwrap();
+    let uri = url_from_abs_path(&file_name);
 
     // FIXME: this doesn't handle UTF16 offsets correctly
     let range = Range::new(
@@ -176,6 +182,7 @@ pub(crate) struct MappedRustDiagnostic {
 ///
 /// If the diagnostic has no primary span this will return `None`
 pub(crate) fn map_rust_diagnostic_to_lsp(
+    config: &DiagnosticsConfig,
     rd: &ra_flycheck::Diagnostic,
     workspace_root: &Path,
 ) -> Vec<MappedRustDiagnostic> {
@@ -184,7 +191,7 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
         return Vec::new();
     }
 
-    let mut severity = map_level_to_severity(rd.level);
+    let severity = map_diagnostic_to_severity(config, rd);
 
     let mut source = String::from("rustc");
     let mut code = rd.code.as_ref().map(|c| c.code.clone());
@@ -226,7 +233,6 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
     }
 
     if is_unused_or_unnecessary(rd) {
-        severity = Some(DiagnosticSeverity::Hint);
         tags.push(DiagnosticTag::Unnecessary);
     }
 
@@ -275,70 +281,16 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
         .collect()
 }
 
-/// Returns a `Url` object from a given path, will lowercase drive letters if present.
-/// This will only happen when processing windows paths.
-///
-/// When processing non-windows path, this is essentially the same as `Url::from_file_path`.
-pub fn url_from_path_with_drive_lowercasing(path: impl AsRef<Path>) -> Result<Url> {
-    let component_has_windows_drive = path.as_ref().components().any(|comp| {
-        if let Component::Prefix(c) = comp {
-            return matches!(c.kind(), Prefix::Disk(_) | Prefix::VerbatimDisk(_));
-        }
-        false
-    });
-
-    // VSCode expects drive letters to be lowercased, where rust will uppercase the drive letters.
-    let res = if component_has_windows_drive {
-        let url_original = Url::from_file_path(&path)
-            .map_err(|_| format!("can't convert path to url: {}", path.as_ref().display()))?;
-
-        let drive_partition: Vec<&str> = url_original.as_str().rsplitn(2, ':').collect();
-
-        // There is a drive partition, but we never found a colon.
-        // This should not happen, but in this case we just pass it through.
-        if drive_partition.len() == 1 {
-            return Ok(url_original);
-        }
-
-        let joined = drive_partition[1].to_ascii_lowercase() + ":" + drive_partition[0];
-        let url = Url::from_str(&joined).expect("This came from a valid `Url`");
-
-        url
-    } else {
-        Url::from_file_path(&path)
-            .map_err(|_| format!("can't convert path to url: {}", path.as_ref().display()))?
-    };
-    Ok(res)
-}
-
 #[cfg(test)]
+#[cfg(not(windows))]
 mod tests {
     use super::*;
 
-    // `Url` is not able to parse windows paths on unix machines.
-    #[test]
-    #[cfg(target_os = "windows")]
-    fn test_lowercase_drive_letter_with_drive() {
-        let url = url_from_path_with_drive_lowercasing("C:\\Test").unwrap();
-
-        assert_eq!(url.to_string(), "file:///c:/Test");
-    }
-
-    #[test]
-    #[cfg(target_os = "windows")]
-    fn test_drive_without_colon_passthrough() {
-        let url = url_from_path_with_drive_lowercasing(r#"\\localhost\C$\my_dir"#).unwrap();
-
-        assert_eq!(url.to_string(), "file://localhost/C$/my_dir");
-    }
-
-    #[cfg(not(windows))]
     fn parse_diagnostic(val: &str) -> ra_flycheck::Diagnostic {
         serde_json::from_str::<ra_flycheck::Diagnostic>(val).unwrap()
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_rustc_incompatible_type_for_trait() {
         let diag = parse_diagnostic(
             r##"{
@@ -387,12 +339,11 @@ mod tests {
         );
 
         let workspace_root = Path::new("/test/");
-        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        let diag = map_rust_diagnostic_to_lsp(&DiagnosticsConfig::default(), &diag, workspace_root);
         insta::assert_debug_snapshot!(diag);
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_rustc_unused_variable() {
         let diag = parse_diagnostic(
             r##"{
@@ -470,12 +421,187 @@ mod tests {
         );
 
         let workspace_root = Path::new("/test/");
-        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        let diag = map_rust_diagnostic_to_lsp(&DiagnosticsConfig::default(), &diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_rustc_unused_variable_as_info() {
+        let diag = parse_diagnostic(
+            r##"{
+    "message": "unused variable: `foo`",
+    "code": {
+        "code": "unused_variables",
+        "explanation": null
+    },
+    "level": "warning",
+    "spans": [
+        {
+            "file_name": "driver/subcommand/repl.rs",
+            "byte_start": 9228,
+            "byte_end": 9231,
+            "line_start": 291,
+            "line_end": 291,
+            "column_start": 9,
+            "column_end": 12,
+            "is_primary": true,
+            "text": [
+                {
+                    "text": "    let foo = 42;",
+                    "highlight_start": 9,
+                    "highlight_end": 12
+                }
+            ],
+            "label": null,
+            "suggested_replacement": null,
+            "suggestion_applicability": null,
+            "expansion": null
+        }
+    ],
+    "children": [
+        {
+            "message": "#[warn(unused_variables)] on by default",
+            "code": null,
+            "level": "note",
+            "spans": [],
+            "children": [],
+            "rendered": null
+        },
+        {
+            "message": "consider prefixing with an underscore",
+            "code": null,
+            "level": "help",
+            "spans": [
+                {
+                    "file_name": "driver/subcommand/repl.rs",
+                    "byte_start": 9228,
+                    "byte_end": 9231,
+                    "line_start": 291,
+                    "line_end": 291,
+                    "column_start": 9,
+                    "column_end": 12,
+                    "is_primary": true,
+                    "text": [
+                        {
+                            "text": "    let foo = 42;",
+                            "highlight_start": 9,
+                            "highlight_end": 12
+                        }
+                    ],
+                    "label": null,
+                    "suggested_replacement": "_foo",
+                    "suggestion_applicability": "MachineApplicable",
+                    "expansion": null
+                }
+            ],
+            "children": [],
+            "rendered": null
+        }
+    ],
+    "rendered": "warning: unused variable: `foo`\n   --> driver/subcommand/repl.rs:291:9\n    |\n291 |     let foo = 42;\n    |         ^^^ help: consider prefixing with an underscore: `_foo`\n    |\n    = note: #[warn(unused_variables)] on by default\n\n"
+    }"##,
+        );
+
+        let config = DiagnosticsConfig {
+            warnings_as_info: vec!["unused_variables".to_string()],
+            ..DiagnosticsConfig::default()
+        };
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&config, &diag, workspace_root);
         insta::assert_debug_snapshot!(diag);
     }
 
     #[test]
     #[cfg(not(windows))]
+    fn snap_rustc_unused_variable_as_hint() {
+        let diag = parse_diagnostic(
+            r##"{
+    "message": "unused variable: `foo`",
+    "code": {
+        "code": "unused_variables",
+        "explanation": null
+    },
+    "level": "warning",
+    "spans": [
+        {
+            "file_name": "driver/subcommand/repl.rs",
+            "byte_start": 9228,
+            "byte_end": 9231,
+            "line_start": 291,
+            "line_end": 291,
+            "column_start": 9,
+            "column_end": 12,
+            "is_primary": true,
+            "text": [
+                {
+                    "text": "    let foo = 42;",
+                    "highlight_start": 9,
+                    "highlight_end": 12
+                }
+            ],
+            "label": null,
+            "suggested_replacement": null,
+            "suggestion_applicability": null,
+            "expansion": null
+        }
+    ],
+    "children": [
+        {
+            "message": "#[warn(unused_variables)] on by default",
+            "code": null,
+            "level": "note",
+            "spans": [],
+            "children": [],
+            "rendered": null
+        },
+        {
+            "message": "consider prefixing with an underscore",
+            "code": null,
+            "level": "help",
+            "spans": [
+                {
+                    "file_name": "driver/subcommand/repl.rs",
+                    "byte_start": 9228,
+                    "byte_end": 9231,
+                    "line_start": 291,
+                    "line_end": 291,
+                    "column_start": 9,
+                    "column_end": 12,
+                    "is_primary": true,
+                    "text": [
+                        {
+                            "text": "    let foo = 42;",
+                            "highlight_start": 9,
+                            "highlight_end": 12
+                        }
+                    ],
+                    "label": null,
+                    "suggested_replacement": "_foo",
+                    "suggestion_applicability": "MachineApplicable",
+                    "expansion": null
+                }
+            ],
+            "children": [],
+            "rendered": null
+        }
+    ],
+    "rendered": "warning: unused variable: `foo`\n   --> driver/subcommand/repl.rs:291:9\n    |\n291 |     let foo = 42;\n    |         ^^^ help: consider prefixing with an underscore: `_foo`\n    |\n    = note: #[warn(unused_variables)] on by default\n\n"
+    }"##,
+        );
+
+        let config = DiagnosticsConfig {
+            warnings_as_hint: vec!["unused_variables".to_string()],
+            ..DiagnosticsConfig::default()
+        };
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&config, &diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
     fn snap_rustc_wrong_number_of_parameters() {
         let diag = parse_diagnostic(
             r##"{
@@ -595,12 +721,11 @@ mod tests {
         );
 
         let workspace_root = Path::new("/test/");
-        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        let diag = map_rust_diagnostic_to_lsp(&DiagnosticsConfig::default(), &diag, workspace_root);
         insta::assert_debug_snapshot!(diag);
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_clippy_pass_by_ref() {
         let diag = parse_diagnostic(
             r##"{
@@ -716,12 +841,11 @@ mod tests {
         );
 
         let workspace_root = Path::new("/test/");
-        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        let diag = map_rust_diagnostic_to_lsp(&DiagnosticsConfig::default(), &diag, workspace_root);
         insta::assert_debug_snapshot!(diag);
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_rustc_mismatched_type() {
         let diag = parse_diagnostic(
             r##"{
@@ -760,12 +884,11 @@ mod tests {
         );
 
         let workspace_root = Path::new("/test/");
-        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        let diag = map_rust_diagnostic_to_lsp(&DiagnosticsConfig::default(), &diag, workspace_root);
         insta::assert_debug_snapshot!(diag);
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_handles_macro_location() {
         let diag = parse_diagnostic(
             r##"{
@@ -1032,12 +1155,11 @@ mod tests {
         );
 
         let workspace_root = Path::new("/test/");
-        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        let diag = map_rust_diagnostic_to_lsp(&DiagnosticsConfig::default(), &diag, workspace_root);
         insta::assert_debug_snapshot!(diag);
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_macro_compiler_error() {
         let diag = parse_diagnostic(
             r##"{
@@ -1262,12 +1384,11 @@ mod tests {
         );
 
         let workspace_root = Path::new("/test/");
-        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        let diag = map_rust_diagnostic_to_lsp(&DiagnosticsConfig::default(), &diag, workspace_root);
         insta::assert_debug_snapshot!(diag);
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_multi_line_fix() {
         let diag = parse_diagnostic(
             r##"{
@@ -1396,7 +1517,7 @@ mod tests {
         );
 
         let workspace_root = Path::new("/test/");
-        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        let diag = map_rust_diagnostic_to_lsp(&DiagnosticsConfig::default(), &diag, workspace_root);
         insta::assert_debug_snapshot!(diag);
     }
 }
diff --git a/crates/rust-analyzer/src/from_proto.rs b/crates/rust-analyzer/src/from_proto.rs
index 206673829..40f856e6e 100644
--- a/crates/rust-analyzer/src/from_proto.rs
+++ b/crates/rust-analyzer/src/from_proto.rs
@@ -17,7 +17,7 @@ pub(crate) fn text_range(line_index: &LineIndex, range: lsp_types::Range) -> Tex
 }
 
 pub(crate) fn file_id(world: &GlobalStateSnapshot, url: &lsp_types::Url) -> Result<FileId> {
-    world.uri_to_file_id(url)
+    world.url_to_file_id(url)
 }
 
 pub(crate) fn file_position(
diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index 21116e165..1527c9947 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -12,42 +12,34 @@ use crossbeam_channel::{unbounded, Receiver};
 use lsp_types::Url;
 use parking_lot::RwLock;
 use ra_flycheck::{Flycheck, FlycheckConfig};
-use ra_ide::{
-    Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, LibraryData, SourceRootId,
-};
-use ra_project_model::{ProcMacroClient, ProjectWorkspace};
-use ra_vfs::{LineEndings, RootEntry, Vfs, VfsChange, VfsFile, VfsRoot, VfsTask, Watch};
-use relative_path::RelativePathBuf;
+use ra_ide::{Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, SourceRootId};
+use ra_project_model::{CargoWorkspace, ProcMacroClient, ProjectWorkspace, Target};
+use ra_vfs::{LineEndings, RootEntry, Vfs, VfsChange, VfsFile, VfsTask, Watch};
 use stdx::format_to;
 
 use crate::{
-    config::Config,
-    diagnostics::{
-        to_proto::url_from_path_with_drive_lowercasing, CheckFixes, DiagnosticCollection,
-    },
+    config::{Config, FilesWatcher},
+    diagnostics::{CheckFixes, DiagnosticCollection},
     main_loop::pending_requests::{CompletedRequest, LatestRequests},
+    to_proto::url_from_abs_path,
     vfs_glob::{Glob, RustPackageFilterBuilder},
     LspError, Result,
 };
-use ra_db::ExternSourceId;
+use ra_db::{CrateId, ExternSourceId};
 use rustc_hash::{FxHashMap, FxHashSet};
 
 fn create_flycheck(workspaces: &[ProjectWorkspace], config: &FlycheckConfig) -> Option<Flycheck> {
     // FIXME: Figure out the multi-workspace situation
-    workspaces
-        .iter()
-        .find_map(|w| match w {
-            ProjectWorkspace::Cargo { cargo, .. } => Some(cargo),
-            ProjectWorkspace::Json { .. } => None,
-        })
-        .map(|cargo| {
+    workspaces.iter().find_map(|w| match w {
+        ProjectWorkspace::Cargo { cargo, .. } => {
             let cargo_project_root = cargo.workspace_root().to_path_buf();
             Some(Flycheck::new(config.clone(), cargo_project_root))
-        })
-        .unwrap_or_else(|| {
+        }
+        ProjectWorkspace::Json { .. } => {
             log::warn!("Cargo check watching only supported for cargo workspaces, disabling");
             None
-        })
+        }
+    })
 }
 
 /// `GlobalState` is the primary mutable state of the language server
@@ -84,7 +76,6 @@ impl GlobalState {
         workspaces: Vec<ProjectWorkspace>,
         lru_capacity: Option<usize>,
         exclude_globs: &[Glob],
-        watch: Watch,
         config: Config,
     ) -> GlobalState {
         let mut change = AnalysisChange::new();
@@ -119,6 +110,7 @@ impl GlobalState {
 
         let (task_sender, task_receiver) = unbounded();
         let task_sender = Box::new(move |t| task_sender.send(t).unwrap());
+        let watch = Watch(matches!(config.files.watcher, FilesWatcher::Notify));
         let (mut vfs, vfs_roots) = Vfs::new(roots, task_sender, watch);
 
         let mut extern_source_roots = FxHashMap::default();
@@ -196,32 +188,18 @@ impl GlobalState {
 
     /// Returns a vec of libraries
     /// FIXME: better API here
-    pub fn process_changes(
-        &mut self,
-        roots_scanned: &mut usize,
-    ) -> Option<Vec<(SourceRootId, Vec<(FileId, RelativePathBuf, Arc<String>)>)>> {
+    pub fn process_changes(&mut self, roots_scanned: &mut usize) -> bool {
         let changes = self.vfs.write().commit_changes();
         if changes.is_empty() {
-            return None;
+            return false;
         }
-        let mut libs = Vec::new();
         let mut change = AnalysisChange::new();
         for c in changes {
             match c {
                 VfsChange::AddRoot { root, files } => {
-                    let root_path = self.vfs.read().root2path(root);
-                    let is_local = self.local_roots.iter().any(|r| root_path.starts_with(r));
-                    if is_local {
-                        *roots_scanned += 1;
-                        for (file, path, text) in files {
-                            change.add_file(SourceRootId(root.0), FileId(file.0), path, text);
-                        }
-                    } else {
-                        let files = files
-                            .into_iter()
-                            .map(|(vfsfile, path, text)| (FileId(vfsfile.0), path, text))
-                            .collect();
-                        libs.push((SourceRootId(root.0), files));
+                    *roots_scanned += 1;
+                    for (file, path, text) in files {
+                        change.add_file(SourceRootId(root.0), FileId(file.0), path, text);
                     }
                 }
                 VfsChange::AddFile { root, file, path, text } => {
@@ -236,13 +214,7 @@ impl GlobalState {
             }
         }
         self.analysis_host.apply_change(change);
-        Some(libs)
-    }
-
-    pub fn add_lib(&mut self, data: LibraryData) {
-        let mut change = AnalysisChange::new();
-        change.add_library(data);
-        self.analysis_host.apply_change(change);
+        true
     }
 
     pub fn snapshot(&self) -> GlobalStateSnapshot {
@@ -274,8 +246,8 @@ impl GlobalStateSnapshot {
         &self.analysis
     }
 
-    pub fn uri_to_file_id(&self, uri: &Url) -> Result<FileId> {
-        let path = uri.to_file_path().map_err(|()| format!("invalid uri: {}", uri))?;
+    pub fn url_to_file_id(&self, url: &Url) -> Result<FileId> {
+        let path = url.to_file_path().map_err(|()| format!("invalid uri: {}", url))?;
         let file = self.vfs.read().path2file(&path).ok_or_else(|| {
             // Show warning as this file is outside current workspace
             // FIXME: just handle such files, and remove `LspError::UNKNOWN_FILE`.
@@ -287,27 +259,33 @@ impl GlobalStateSnapshot {
         Ok(FileId(file.0))
     }
 
-    pub fn file_id_to_uri(&self, id: FileId) -> Result<Url> {
-        let path = self.vfs.read().file2path(VfsFile(id.0));
-        let url = url_from_path_with_drive_lowercasing(path)?;
-
-        Ok(url)
-    }
-
-    pub fn file_id_to_path(&self, id: FileId) -> PathBuf {
-        self.vfs.read().file2path(VfsFile(id.0))
+    pub fn file_id_to_url(&self, id: FileId) -> Url {
+        file_id_to_url(&self.vfs.read(), id)
     }
 
     pub fn file_line_endings(&self, id: FileId) -> LineEndings {
         self.vfs.read().file_line_endings(VfsFile(id.0))
     }
 
-    pub fn path_to_uri(&self, root: SourceRootId, path: &RelativePathBuf) -> Result<Url> {
-        let base = self.vfs.read().root2path(VfsRoot(root.0));
-        let path = path.to_path(base);
-        let url = Url::from_file_path(&path)
-            .map_err(|_| format!("can't convert path to url: {}", path.display()))?;
-        Ok(url)
+    pub fn anchored_path(&self, file_id: FileId, path: &str) -> Url {
+        let mut base = self.vfs.read().file2path(VfsFile(file_id.0));
+        base.pop();
+        let path = base.join(path);
+        url_from_abs_path(&path)
+    }
+
+    pub(crate) fn cargo_target_for_crate_root(
+        &self,
+        crate_id: CrateId,
+    ) -> Option<(&CargoWorkspace, Target)> {
+        let file_id = self.analysis().crate_root(crate_id).ok()?;
+        let path = self.vfs.read().file2path(VfsFile(file_id.0));
+        self.workspaces.iter().find_map(|ws| match ws {
+            ProjectWorkspace::Cargo { cargo, .. } => {
+                cargo.target_by_root(&path).map(|it| (cargo, it))
+            }
+            ProjectWorkspace::Json { .. } => None,
+        })
     }
 
     pub fn status(&self) -> String {
@@ -335,3 +313,8 @@ impl GlobalStateSnapshot {
         self.workspaces.iter().find_map(|ws| ws.workspace_root_for(&path))
     }
 }
+
+pub(crate) fn file_id_to_url(vfs: &Vfs, id: FileId) -> Url {
+    let path = vfs.file2path(VfsFile(id.0));
+    url_from_abs_path(&path)
+}
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 752dbf145..f0aaaa21e 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -24,20 +24,19 @@ use lsp_types::{
     WorkDoneProgressReport,
 };
 use ra_flycheck::{CheckTask, Status};
-use ra_ide::{Canceled, FileId, LibraryData, LineIndex, SourceRootId};
+use ra_ide::{Canceled, FileId, LineIndex};
 use ra_prof::profile;
 use ra_project_model::{PackageRoot, ProjectWorkspace};
-use ra_vfs::{VfsFile, VfsTask, Watch};
-use relative_path::RelativePathBuf;
+use ra_vfs::VfsTask;
 use rustc_hash::FxHashSet;
 use serde::{de::DeserializeOwned, Serialize};
 use threadpool::ThreadPool;
 
 use crate::{
     config::{Config, FilesWatcher, LinkedProject},
-    diagnostics::{to_proto::url_from_path_with_drive_lowercasing, DiagnosticTask},
+    diagnostics::DiagnosticTask,
     from_proto,
-    global_state::{GlobalState, GlobalStateSnapshot},
+    global_state::{file_id_to_url, GlobalState, GlobalStateSnapshot},
     lsp_ext,
     main_loop::{
         pending_requests::{PendingRequest, PendingRequests},
@@ -121,7 +120,12 @@ pub fn main_loop(config: Config, connection: Connection) -> Result<()> {
                         })
                         .ok()
                     }
-                    LinkedProject::JsonProject(it) => Some(it.clone().into()),
+                    LinkedProject::InlineJsonProject(it) => {
+                        Some(ra_project_model::ProjectWorkspace::Json {
+                            project: it.clone(),
+                            project_location: config.root_path.clone(),
+                        })
+                    }
                 })
                 .collect::<Vec<_>>()
         };
@@ -156,25 +160,17 @@ pub fn main_loop(config: Config, connection: Connection) -> Result<()> {
             connection.sender.send(request.into()).unwrap();
         }
 
-        GlobalState::new(
-            workspaces,
-            config.lru_capacity,
-            &globs,
-            Watch(matches!(config.files.watcher, FilesWatcher::Notify)),
-            config,
-        )
+        GlobalState::new(workspaces, config.lru_capacity, &globs, config)
     };
 
     loop_state.roots_total = global_state.vfs.read().n_roots();
 
     let pool = ThreadPool::default();
     let (task_sender, task_receiver) = unbounded::<Task>();
-    let (libdata_sender, libdata_receiver) = unbounded::<LibraryData>();
 
     log::info!("server initialized, serving requests");
     {
         let task_sender = task_sender;
-        let libdata_sender = libdata_sender;
         loop {
             log::trace!("selecting");
             let event = select! {
@@ -187,7 +183,6 @@ pub fn main_loop(config: Config, connection: Connection) -> Result<()> {
                     Ok(task) => Event::Vfs(task),
                     Err(RecvError) => return Err("vfs died".into()),
                 },
-                recv(libdata_receiver) -> data => Event::Lib(data.unwrap()),
                 recv(global_state.flycheck.as_ref().map_or(&never(), |it| &it.task_recv)) -> task => match task {
                     Ok(task) => Event::CheckWatcher(task),
                     Err(RecvError) => return Err("check watcher died".into()),
@@ -198,15 +193,7 @@ pub fn main_loop(config: Config, connection: Connection) -> Result<()> {
                     break;
                 };
             }
-            loop_turn(
-                &pool,
-                &task_sender,
-                &libdata_sender,
-                &connection,
-                &mut global_state,
-                &mut loop_state,
-                event,
-            )?;
+            loop_turn(&pool, &task_sender, &connection, &mut global_state, &mut loop_state, event)?;
         }
     }
     global_state.analysis_host.request_cancellation();
@@ -214,7 +201,6 @@ pub fn main_loop(config: Config, connection: Connection) -> Result<()> {
     task_receiver.into_iter().for_each(|task| {
         on_task(task, &connection.sender, &mut loop_state.pending_requests, &mut global_state)
     });
-    libdata_receiver.into_iter().for_each(drop);
     log::info!("...tasks have finished");
     log::info!("joining threadpool...");
     pool.join();
@@ -238,7 +224,6 @@ enum Event {
     Msg(Message),
     Task(Task),
     Vfs(VfsTask),
-    Lib(LibraryData),
     CheckWatcher(CheckTask),
 }
 
@@ -274,7 +259,6 @@ impl fmt::Debug for Event {
             Event::Msg(it) => fmt::Debug::fmt(it, f),
             Event::Task(it) => fmt::Debug::fmt(it, f),
             Event::Vfs(it) => fmt::Debug::fmt(it, f),
-            Event::Lib(it) => fmt::Debug::fmt(it, f),
             Event::CheckWatcher(it) => fmt::Debug::fmt(it, f),
         }
     }
@@ -286,10 +270,6 @@ struct LoopState {
     pending_responses: FxHashSet<RequestId>,
     pending_requests: PendingRequests,
     subscriptions: Subscriptions,
-    // We try not to index more than MAX_IN_FLIGHT_LIBS libraries at the same
-    // time to always have a thread ready to react to input.
-    in_flight_libraries: usize,
-    pending_libraries: Vec<(SourceRootId, Vec<(FileId, RelativePathBuf, Arc<String>)>)>,
     workspace_loaded: bool,
     roots_progress_reported: Option<usize>,
     roots_scanned: usize,
@@ -310,7 +290,6 @@ impl LoopState {
 fn loop_turn(
     pool: &ThreadPool,
     task_sender: &Sender<Task>,
-    libdata_sender: &Sender<LibraryData>,
     connection: &Connection,
     global_state: &mut GlobalState,
     loop_state: &mut LoopState,
@@ -334,12 +313,6 @@ fn loop_turn(
         Event::Vfs(task) => {
             global_state.vfs.write().handle_task(task);
         }
-        Event::Lib(lib) => {
-            global_state.add_lib(lib);
-            global_state.maybe_collect_garbage();
-            loop_state.in_flight_libraries -= 1;
-            loop_state.roots_scanned += 1;
-        }
         Event::CheckWatcher(task) => on_check_task(task, global_state, task_sender)?,
         Event::Msg(msg) => match msg {
             Message::Request(req) => on_request(
@@ -385,36 +358,12 @@ fn loop_turn(
         },
     };
 
-    let mut state_changed = false;
-    if let Some(changes) = global_state.process_changes(&mut loop_state.roots_scanned) {
-        state_changed = true;
-        loop_state.pending_libraries.extend(changes);
-    }
-
-    let max_in_flight_libs = pool.max_count().saturating_sub(2).max(1);
-    while loop_state.in_flight_libraries < max_in_flight_libs {
-        let (root, files) = match loop_state.pending_libraries.pop() {
-            Some(it) => it,
-            None => break,
-        };
-
-        loop_state.in_flight_libraries += 1;
-        let sender = libdata_sender.clone();
-        pool.execute(move || {
-            log::info!("indexing {:?} ... ", root);
-            let data = LibraryData::prepare(root, files);
-            sender.send(data).unwrap();
-        });
-    }
+    let mut state_changed = global_state.process_changes(&mut loop_state.roots_scanned);
 
     let show_progress =
         !loop_state.workspace_loaded && global_state.config.client_caps.work_done_progress;
 
-    if !loop_state.workspace_loaded
-        && loop_state.roots_scanned == loop_state.roots_total
-        && loop_state.pending_libraries.is_empty()
-        && loop_state.in_flight_libraries == 0
-    {
+    if !loop_state.workspace_loaded && loop_state.roots_scanned == loop_state.roots_total {
         state_changed = true;
         loop_state.workspace_loaded = true;
         if let Some(flycheck) = &global_state.flycheck {
@@ -664,14 +613,11 @@ fn apply_document_changes(
     mut line_index: Cow<'_, LineIndex>,
     content_changes: Vec<TextDocumentContentChangeEvent>,
 ) {
-    // Remove when https://github.com/rust-analyzer/rust-analyzer/issues/4263 is fixed.
-    let backup_text = old_text.clone();
-    let backup_changes = content_changes.clone();
-
     // The changes we got must be applied sequentially, but can cross lines so we
     // have to keep our line index updated.
     // Some clients (e.g. Code) sort the ranges in reverse. As an optimization, we
     // remember the last valid line in the index and only rebuild it if needed.
+    // The VFS will normalize the end of lines to `\n`.
     enum IndexValid {
         All,
         UpToLineExclusive(u64),
@@ -695,19 +641,7 @@ fn apply_document_changes(
                 }
                 index_valid = IndexValid::UpToLineExclusive(range.start.line);
                 let range = from_proto::text_range(&line_index, range);
-                let mut text = old_text.to_owned();
-                match std::panic::catch_unwind(move || {
-                    text.replace_range(Range::<usize>::from(range), &change.text);
-                    text
-                }) {
-                    Ok(t) => *old_text = t,
-                    Err(e) => {
-                        eprintln!("Bug in incremental text synchronization. Please report the following output on https://github.com/rust-analyzer/rust-analyzer/issues/4263");
-                        dbg!(&backup_text);
-                        dbg!(&backup_changes);
-                        std::panic::resume_unwind(e);
-                    }
-                }
+                old_text.replace_range(Range::<usize>::from(range), &change.text);
             }
             None => {
                 *old_text = change.text;
@@ -729,6 +663,7 @@ fn on_check_task(
 
         CheckTask::AddDiagnostic { workspace_root, diagnostic } => {
             let diagnostics = crate::diagnostics::to_proto::map_rust_diagnostic_to_lsp(
+                &global_state.config.diagnostics,
                 &diagnostic,
                 &workspace_root,
             );
@@ -801,17 +736,9 @@ fn on_diagnostic_task(task: DiagnosticTask, msg_sender: &Sender<Message>, state:
     let subscriptions = state.diagnostics.handle_task(task);
 
     for file_id in subscriptions {
-        let path = state.vfs.read().file2path(VfsFile(file_id.0));
-        let uri = match url_from_path_with_drive_lowercasing(&path) {
-            Ok(uri) => uri,
-            Err(err) => {
-                log::error!("Couldn't convert path to url ({}): {}", err, path.display());
-                continue;
-            }
-        };
-
+        let url = file_id_to_url(&state.vfs.read(), file_id);
         let diagnostics = state.diagnostics.diagnostics_for(file_id).cloned().collect();
-        let params = lsp_types::PublishDiagnosticsParams { uri, diagnostics, version: None };
+        let params = lsp_types::PublishDiagnosticsParams { uri: url, diagnostics, version: None };
         let not = notification_new::<lsp_types::notification::PublishDiagnostics>(params);
         msg_sender.send(not.into()).unwrap();
     }
diff --git a/crates/rust-analyzer/src/main_loop/handlers.rs b/crates/rust-analyzer/src/main_loop/handlers.rs
index a41adf8b0..2d7e649d2 100644
--- a/crates/rust-analyzer/src/main_loop/handlers.rs
+++ b/crates/rust-analyzer/src/main_loop/handlers.rs
@@ -18,8 +18,8 @@ use lsp_types::{
     TextDocumentIdentifier, Url, WorkspaceEdit,
 };
 use ra_ide::{
-    FileId, FilePosition, FileRange, HoverAction, Query, RangeInfo, Runnable, RunnableKind,
-    SearchScope, TextEdit,
+    FileId, FilePosition, FileRange, HoverAction, HoverGotoTypeData, NavigationTarget, Query,
+    RangeInfo, Runnable, RunnableKind, SearchScope, TextEdit,
 };
 use ra_prof::profile;
 use ra_project_model::TargetKind;
@@ -258,7 +258,7 @@ pub fn handle_document_symbol(
     let res = if snap.config.client_caps.hierarchical_symbols {
         document_symbols.into()
     } else {
-        let url = to_proto::url(&snap, file_id)?;
+        let url = to_proto::url(&snap, file_id);
         let mut symbol_information = Vec::<SymbolInformation>::new();
         for symbol in document_symbols {
             flatten_document_symbol(&symbol, None, &url, &mut symbol_information);
@@ -1150,6 +1150,23 @@ fn debug_single_command(runnable: &lsp_ext::Runnable) -> Command {
     }
 }
 
+fn goto_location_command(snap: &GlobalStateSnapshot, nav: &NavigationTarget) -> Option<Command> {
+    let value = if snap.config.client_caps.location_link {
+        let link = to_proto::location_link(snap, None, nav.clone()).ok()?;
+        to_value(link).ok()?
+    } else {
+        let range = FileRange { file_id: nav.file_id(), range: nav.range() };
+        let location = to_proto::location(snap, range).ok()?;
+        to_value(location).ok()?
+    };
+
+    Some(Command {
+        title: nav.name().to_string(),
+        command: "rust-analyzer.gotoLocation".into(),
+        arguments: Some(vec![value]),
+    })
+}
+
 fn to_command_link(command: Command, tooltip: String) -> lsp_ext::CommandLink {
     lsp_ext::CommandLink { tooltip: Some(tooltip), command }
 }
@@ -1160,7 +1177,7 @@ fn show_impl_command_link(
 ) -> Option<lsp_ext::CommandLinkGroup> {
     if snap.config.hover.implementations {
         if let Some(nav_data) = snap.analysis().goto_implementation(*position).unwrap_or(None) {
-            let uri = to_proto::url(snap, position.file_id).ok()?;
+            let uri = to_proto::url(snap, position.file_id);
             let line_index = snap.analysis().file_line_index(position.file_id).ok()?;
             let position = to_proto::position(&line_index, position.offset);
             let locations: Vec<_> = nav_data
@@ -1180,13 +1197,13 @@ fn show_impl_command_link(
     None
 }
 
-fn to_runnable_action(
+fn runnable_action_links(
     snap: &GlobalStateSnapshot,
     file_id: FileId,
     runnable: Runnable,
 ) -> Option<lsp_ext::CommandLinkGroup> {
     let cargo_spec = CargoTargetSpec::for_file(&snap, file_id).ok()?;
-    if should_skip_target(&runnable, cargo_spec.as_ref()) {
+    if !snap.config.hover.runnable() || should_skip_target(&runnable, cargo_spec.as_ref()) {
         return None;
     }
 
@@ -1208,6 +1225,26 @@ fn to_runnable_action(
     })
 }
 
+fn goto_type_action_links(
+    snap: &GlobalStateSnapshot,
+    nav_targets: &[HoverGotoTypeData],
+) -> Option<lsp_ext::CommandLinkGroup> {
+    if !snap.config.hover.goto_type_def || nav_targets.is_empty() {
+        return None;
+    }
+
+    Some(lsp_ext::CommandLinkGroup {
+        title: Some("Go to ".into()),
+        commands: nav_targets
+            .iter()
+            .filter_map(|it| {
+                goto_location_command(snap, &it.nav)
+                    .map(|cmd| to_command_link(cmd, it.mod_path.clone()))
+            })
+            .collect(),
+    })
+}
+
 fn prepare_hover_actions(
     snap: &GlobalStateSnapshot,
     file_id: FileId,
@@ -1221,7 +1258,8 @@ fn prepare_hover_actions(
         .iter()
         .filter_map(|it| match it {
             HoverAction::Implementaion(position) => show_impl_command_link(snap, position),
-            HoverAction::Runnable(r) => to_runnable_action(snap, file_id, r.clone()),
+            HoverAction::Runnable(r) => runnable_action_links(snap, file_id, r.clone()),
+            HoverAction::GoToType(targets) => goto_type_action_links(snap, targets),
         })
         .collect()
 }
diff --git a/crates/rust-analyzer/src/semantic_tokens.rs b/crates/rust-analyzer/src/semantic_tokens.rs
index 6f125c37c..2ea63d33b 100644
--- a/crates/rust-analyzer/src/semantic_tokens.rs
+++ b/crates/rust-analyzer/src/semantic_tokens.rs
@@ -45,6 +45,7 @@ define_semantic_token_types![
     (UNION, "union"),
     (UNRESOLVED_REFERENCE, "unresolvedReference"),
     (FORMAT_SPECIFIER, "formatSpecifier"),
+    (ESCAPE_SEQUENCE, "escapeSequence"),
 ];
 
 macro_rules! define_semantic_token_modifiers {
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index 710df1fbd..ec153097e 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -1,4 +1,7 @@
 //! Conversion of rust-analyzer specific types to lsp_types equivalents.
+use std::path::{self, Path};
+
+use itertools::Itertools;
 use ra_db::{FileId, FileRange};
 use ra_ide::{
     Assist, CompletionItem, CompletionItemKind, Documentation, FileSystemEdit, Fold, FoldKind,
@@ -321,12 +324,14 @@ fn semantic_token_type_and_modifiers(
         HighlightTag::UnresolvedReference => semantic_tokens::UNRESOLVED_REFERENCE,
         HighlightTag::FormatSpecifier => semantic_tokens::FORMAT_SPECIFIER,
         HighlightTag::Operator => lsp_types::SemanticTokenType::OPERATOR,
+        HighlightTag::EscapeSequence => semantic_tokens::ESCAPE_SEQUENCE,
     };
 
     for modifier in highlight.modifiers.iter() {
         let modifier = match modifier {
             HighlightModifier::Attribute => semantic_tokens::ATTRIBUTE_MODIFIER,
             HighlightModifier::Definition => lsp_types::SemanticTokenModifier::DECLARATION,
+            HighlightModifier::Documentation => lsp_types::SemanticTokenModifier::DOCUMENTATION,
             HighlightModifier::ControlFlow => semantic_tokens::CONTROL_FLOW,
             HighlightModifier::Mutable => semantic_tokens::MUTABLE,
             HighlightModifier::Unsafe => semantic_tokens::UNSAFE,
@@ -385,24 +390,55 @@ pub(crate) fn folding_range(
     }
 }
 
-pub(crate) fn url(snap: &GlobalStateSnapshot, file_id: FileId) -> Result<lsp_types::Url> {
-    snap.file_id_to_uri(file_id)
+pub(crate) fn url(snap: &GlobalStateSnapshot, file_id: FileId) -> lsp_types::Url {
+    snap.file_id_to_url(file_id)
+}
+
+/// Returns a `Url` object from a given path, will lowercase drive letters if present.
+/// This will only happen when processing windows paths.
+///
+/// When processing non-windows path, this is essentially the same as `Url::from_file_path`.
+pub(crate) fn url_from_abs_path(path: &Path) -> lsp_types::Url {
+    assert!(path.is_absolute());
+    let url = lsp_types::Url::from_file_path(path).unwrap();
+    match path.components().next() {
+        Some(path::Component::Prefix(prefix)) if matches!(prefix.kind(), path::Prefix::Disk(_) | path::Prefix::VerbatimDisk(_)) =>
+        {
+            // Need to lowercase driver letter
+        }
+        _ => return url,
+    }
+
+    let driver_letter_range = {
+        let (scheme, drive_letter, _rest) = match url.as_str().splitn(3, ':').collect_tuple() {
+            Some(it) => it,
+            None => return url,
+        };
+        let start = scheme.len() + ':'.len_utf8();
+        start..(start + drive_letter.len())
+    };
+
+    // Note: lowercasing the `path` itself doesn't help, the `Url::parse`
+    // machinery *also* canonicalizes the drive letter. So, just massage the
+    // string in place.
+    let mut url = url.into_string();
+    url[driver_letter_range].make_ascii_lowercase();
+    lsp_types::Url::parse(&url).unwrap()
 }
 
 pub(crate) fn versioned_text_document_identifier(
     snap: &GlobalStateSnapshot,
     file_id: FileId,
     version: Option<i64>,
-) -> Result<lsp_types::VersionedTextDocumentIdentifier> {
-    let res = lsp_types::VersionedTextDocumentIdentifier { uri: url(snap, file_id)?, version };
-    Ok(res)
+) -> lsp_types::VersionedTextDocumentIdentifier {
+    lsp_types::VersionedTextDocumentIdentifier { uri: url(snap, file_id), version }
 }
 
 pub(crate) fn location(
     snap: &GlobalStateSnapshot,
     frange: FileRange,
 ) -> Result<lsp_types::Location> {
-    let url = url(snap, frange.file_id)?;
+    let url = url(snap, frange.file_id);
     let line_index = snap.analysis().file_line_index(frange.file_id)?;
     let range = range(&line_index, frange.range);
     let loc = lsp_types::Location::new(url, range);
@@ -438,7 +474,7 @@ fn location_info(
 ) -> Result<(lsp_types::Url, lsp_types::Range, lsp_types::Range)> {
     let line_index = snap.analysis().file_line_index(target.file_id())?;
 
-    let target_uri = url(snap, target.file_id())?;
+    let target_uri = url(snap, target.file_id());
     let target_range = range(&line_index, target.full_range());
     let target_selection_range =
         target.focus_range().map(|it| range(&line_index, it)).unwrap_or(target_range);
@@ -478,7 +514,7 @@ pub(crate) fn snippet_text_document_edit(
     is_snippet: bool,
     source_file_edit: SourceFileEdit,
 ) -> Result<lsp_ext::SnippetTextDocumentEdit> {
-    let text_document = versioned_text_document_identifier(snap, source_file_edit.file_id, None)?;
+    let text_document = versioned_text_document_identifier(snap, source_file_edit.file_id, None);
     let line_index = snap.analysis().file_line_index(source_file_edit.file_id)?;
     let line_endings = snap.file_line_endings(source_file_edit.file_id);
     let edits = source_file_edit
@@ -492,19 +528,18 @@ pub(crate) fn snippet_text_document_edit(
 pub(crate) fn resource_op(
     snap: &GlobalStateSnapshot,
     file_system_edit: FileSystemEdit,
-) -> Result<lsp_types::ResourceOp> {
-    let res = match file_system_edit {
-        FileSystemEdit::CreateFile { source_root, path } => {
-            let uri = snap.path_to_uri(source_root, &path)?;
+) -> lsp_types::ResourceOp {
+    match file_system_edit {
+        FileSystemEdit::CreateFile { anchor, dst } => {
+            let uri = snap.anchored_path(anchor, &dst);
             lsp_types::ResourceOp::Create(lsp_types::CreateFile { uri, options: None })
         }
-        FileSystemEdit::MoveFile { src, dst_source_root, dst_path } => {
-            let old_uri = snap.file_id_to_uri(src)?;
-            let new_uri = snap.path_to_uri(dst_source_root, &dst_path)?;
+        FileSystemEdit::MoveFile { src, anchor, dst } => {
+            let old_uri = snap.file_id_to_url(src);
+            let new_uri = snap.anchored_path(anchor, &dst);
             lsp_types::ResourceOp::Rename(lsp_types::RenameFile { old_uri, new_uri, options: None })
         }
-    };
-    Ok(res)
+    }
 }
 
 pub(crate) fn snippet_workspace_edit(
@@ -513,7 +548,7 @@ pub(crate) fn snippet_workspace_edit(
 ) -> Result<lsp_ext::SnippetWorkspaceEdit> {
     let mut document_changes: Vec<lsp_ext::SnippetDocumentChangeOperation> = Vec::new();
     for op in source_change.file_system_edits {
-        let op = resource_op(&snap, op)?;
+        let op = resource_op(&snap, op);
         document_changes.push(lsp_ext::SnippetDocumentChangeOperation::Op(op));
     }
     for edit in source_change.source_file_edits {
@@ -568,7 +603,7 @@ impl From<lsp_ext::SnippetWorkspaceEdit> for lsp_types::WorkspaceEdit {
     }
 }
 
-pub fn call_hierarchy_item(
+pub(crate) fn call_hierarchy_item(
     snap: &GlobalStateSnapshot,
     target: NavigationTarget,
 ) -> Result<lsp_types::CallHierarchyItem> {
@@ -579,50 +614,6 @@ pub fn call_hierarchy_item(
     Ok(lsp_types::CallHierarchyItem { name, kind, tags: None, detail, uri, range, selection_range })
 }
 
-#[cfg(test)]
-mod tests {
-    use test_utils::extract_ranges;
-
-    use super::*;
-
-    #[test]
-    fn conv_fold_line_folding_only_fixup() {
-        let text = r#"<fold>mod a;
-mod b;
-mod c;</fold>
-
-fn main() <fold>{
-    if cond <fold>{
-        a::do_a();
-    }</fold> else <fold>{
-        b::do_b();
-    }</fold>
-}</fold>"#;
-
-        let (ranges, text) = extract_ranges(text, "fold");
-        assert_eq!(ranges.len(), 4);
-        let folds = vec![
-            Fold { range: ranges[0], kind: FoldKind::Mods },
-            Fold { range: ranges[1], kind: FoldKind::Block },
-            Fold { range: ranges[2], kind: FoldKind::Block },
-            Fold { range: ranges[3], kind: FoldKind::Block },
-        ];
-
-        let line_index = LineIndex::new(&text);
-        let converted: Vec<lsp_types::FoldingRange> =
-            folds.into_iter().map(|it| folding_range(&text, &line_index, true, it)).collect();
-
-        let expected_lines = [(0, 2), (4, 10), (5, 6), (7, 9)];
-        assert_eq!(converted.len(), expected_lines.len());
-        for (folding_range, (start_line, end_line)) in converted.iter().zip(expected_lines.iter()) {
-            assert_eq!(folding_range.start_line, *start_line);
-            assert_eq!(folding_range.start_character, None);
-            assert_eq!(folding_range.end_line, *end_line);
-            assert_eq!(folding_range.end_character, None);
-        }
-    }
-}
-
 pub(crate) fn unresolved_code_action(
     snap: &GlobalStateSnapshot,
     assist: Assist,
@@ -676,3 +667,62 @@ pub(crate) fn runnable(
         },
     })
 }
+
+#[cfg(test)]
+mod tests {
+    use test_utils::extract_ranges;
+
+    use super::*;
+
+    #[test]
+    fn conv_fold_line_folding_only_fixup() {
+        let text = r#"<fold>mod a;
+mod b;
+mod c;</fold>
+
+fn main() <fold>{
+    if cond <fold>{
+        a::do_a();
+    }</fold> else <fold>{
+        b::do_b();
+    }</fold>
+}</fold>"#;
+
+        let (ranges, text) = extract_ranges(text, "fold");
+        assert_eq!(ranges.len(), 4);
+        let folds = vec![
+            Fold { range: ranges[0], kind: FoldKind::Mods },
+            Fold { range: ranges[1], kind: FoldKind::Block },
+            Fold { range: ranges[2], kind: FoldKind::Block },
+            Fold { range: ranges[3], kind: FoldKind::Block },
+        ];
+
+        let line_index = LineIndex::new(&text);
+        let converted: Vec<lsp_types::FoldingRange> =
+            folds.into_iter().map(|it| folding_range(&text, &line_index, true, it)).collect();
+
+        let expected_lines = [(0, 2), (4, 10), (5, 6), (7, 9)];
+        assert_eq!(converted.len(), expected_lines.len());
+        for (folding_range, (start_line, end_line)) in converted.iter().zip(expected_lines.iter()) {
+            assert_eq!(folding_range.start_line, *start_line);
+            assert_eq!(folding_range.start_character, None);
+            assert_eq!(folding_range.end_line, *end_line);
+            assert_eq!(folding_range.end_character, None);
+        }
+    }
+
+    // `Url` is not able to parse windows paths on unix machines.
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn test_lowercase_drive_letter_with_drive() {
+        let url = url_from_abs_path(Path::new("C:\\Test"));
+        assert_eq!(url.to_string(), "file:///c:/Test");
+    }
+
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn test_drive_without_colon_passthrough() {
+        let url = url_from_abs_path(Path::new(r#"\\localhost\C$\my_dir"#));
+        assert_eq!(url.to_string(), "file://localhost/C$/my_dir");
+    }
+}
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index c0356344c..f2ff0e435 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -1,5 +1,4 @@
 //! Missing batteries for standard libraries.
-
 use std::{cell::Cell, fmt, time::Instant};
 
 #[inline(always)]
diff --git a/crates/test_utils/src/lib.rs b/crates/test_utils/src/lib.rs
index 2141bfc20..981565cd7 100644
--- a/crates/test_utils/src/lib.rs
+++ b/crates/test_utils/src/lib.rs
@@ -10,17 +10,17 @@
 pub mod mark;
 
 use std::{
-    fs,
+    env, fs,
     path::{Path, PathBuf},
 };
 
-pub use ra_cfg::CfgOptions;
+use serde_json::Value;
 use stdx::split1;
+use text_size::{TextRange, TextSize};
 
+pub use ra_cfg::CfgOptions;
 pub use relative_path::{RelativePath, RelativePathBuf};
 pub use rustc_hash::FxHashMap;
-use serde_json::Value;
-use text_size::{TextRange, TextSize};
 
 pub use difference::Changeset as __Changeset;
 
@@ -625,8 +625,6 @@ pub fn skip_slow_tests() -> bool {
     should_skip
 }
 
-const REWRITE: bool = false;
-
 /// Asserts that `expected` and `actual` strings are equal. If they differ only
 /// in trailing or leading whitespace the test won't fail and
 /// the contents of `actual` will be written to the file located at `path`.
@@ -642,7 +640,7 @@ fn assert_equal_text(expected: &str, actual: &str, path: &Path) {
         fs::write(path, actual).unwrap();
         return;
     }
-    if REWRITE {
+    if env::var("UPDATE_EXPECTATIONS").is_ok() {
         println!("rewriting {}", pretty_path.display());
         fs::write(path, actual).unwrap();
         return;
diff --git a/crates/vfs/Cargo.toml b/crates/vfs/Cargo.toml
new file mode 100644
index 000000000..c03e6363b
--- /dev/null
+++ b/crates/vfs/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "vfs"
+version = "0.1.0"
+authors = ["rust-analyzer developers"]
+edition = "2018"
+
+[dependencies]
+rustc-hash = "1.0"
+jod-thread = "0.1.0"
+walkdir = "2.3.1"
+globset = "0.4.5"
+crossbeam-channel = "0.4.0"
+
+paths = { path = "../paths" }
diff --git a/crates/vfs/src/file_set.rs b/crates/vfs/src/file_set.rs
new file mode 100644
index 000000000..724606a3d
--- /dev/null
+++ b/crates/vfs/src/file_set.rs
@@ -0,0 +1,113 @@
+//! Partitions a list of files into disjoint subsets.
+//!
+//! Files which do not belong to any explicitly configured `FileSet` belong to
+//! the default `FileSet`.
+use std::{fmt, iter};
+
+use paths::AbsPathBuf;
+use rustc_hash::FxHashMap;
+
+use crate::{FileId, Vfs, VfsPath};
+
+#[derive(Default, Clone, Eq, PartialEq)]
+pub struct FileSet {
+    files: FxHashMap<VfsPath, FileId>,
+    paths: FxHashMap<FileId, VfsPath>,
+}
+
+impl FileSet {
+    pub fn resolve_path(&self, anchor: FileId, path: &str) -> Option<FileId> {
+        let mut base = self.paths[&anchor].clone();
+        base.pop();
+        let path = base.join(path);
+        let res = self.files.get(&path).copied();
+        res
+    }
+    pub fn insert(&mut self, file_id: FileId, path: VfsPath) {
+        self.files.insert(path.clone(), file_id);
+        self.paths.insert(file_id, path);
+    }
+    pub fn iter(&self) -> impl Iterator<Item = FileId> + '_ {
+        self.paths.keys().copied()
+    }
+}
+
+impl fmt::Debug for FileSet {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("FileSet").field("n_files", &self.files.len()).finish()
+    }
+}
+
+#[derive(Debug)]
+pub struct FileSetConfig {
+    n_file_sets: usize,
+    roots: Vec<(AbsPathBuf, usize)>,
+}
+
+impl Default for FileSetConfig {
+    fn default() -> Self {
+        FileSetConfig::builder().build()
+    }
+}
+
+impl FileSetConfig {
+    pub fn builder() -> FileSetConfigBuilder {
+        FileSetConfigBuilder::default()
+    }
+    pub fn partition(&self, vfs: &Vfs) -> Vec<FileSet> {
+        let mut res = vec![FileSet::default(); self.len()];
+        for (file_id, path) in vfs.iter() {
+            let root = self.classify(&path);
+            res[root].insert(file_id, path)
+        }
+        res
+    }
+    fn len(&self) -> usize {
+        self.n_file_sets
+    }
+    fn classify(&self, path: &VfsPath) -> usize {
+        let path = match path.as_path() {
+            Some(it) => it,
+            None => return self.len() - 1,
+        };
+        let idx = match self.roots.binary_search_by(|(p, _)| p.as_path().cmp(path)) {
+            Ok(it) => it,
+            Err(it) => it.saturating_sub(1),
+        };
+        if path.starts_with(&self.roots[idx].0) {
+            self.roots[idx].1
+        } else {
+            self.len() - 1
+        }
+    }
+}
+
+pub struct FileSetConfigBuilder {
+    roots: Vec<Vec<AbsPathBuf>>,
+}
+
+impl Default for FileSetConfigBuilder {
+    fn default() -> Self {
+        FileSetConfigBuilder { roots: Vec::new() }
+    }
+}
+
+impl FileSetConfigBuilder {
+    pub fn len(&self) -> usize {
+        self.roots.len()
+    }
+    pub fn add_file_set(&mut self, roots: Vec<AbsPathBuf>) {
+        self.roots.push(roots)
+    }
+    pub fn build(self) -> FileSetConfig {
+        let n_file_sets = self.roots.len() + 1;
+        let mut roots: Vec<(AbsPathBuf, usize)> = self
+            .roots
+            .into_iter()
+            .enumerate()
+            .flat_map(|(i, paths)| paths.into_iter().zip(iter::repeat(i)))
+            .collect();
+        roots.sort();
+        FileSetConfig { n_file_sets, roots }
+    }
+}
diff --git a/crates/vfs/src/lib.rs b/crates/vfs/src/lib.rs
new file mode 100644
index 000000000..055219b0c
--- /dev/null
+++ b/crates/vfs/src/lib.rs
@@ -0,0 +1,141 @@
+//! # Virtual File System
+//!
+//! VFS stores all files read by rust-analyzer. Reading file contents from VFS
+//! always returns the same contents, unless VFS was explicitly modified with
+//! `set_file_contents`. All changes to VFS are logged, and can be retrieved via
+//! `take_changes` method. The pack of changes is then pushed to `salsa` and
+//! triggers incremental recomputation.
+//!
+//! Files in VFS are identified with `FileId`s -- interned paths. The notion of
+//! the path, `VfsPath` is somewhat abstract: at the moment, it is represented
+//! as an `std::path::PathBuf` internally, but this is an implementation detail.
+//!
+//! VFS doesn't do IO or file watching itself. For that, see the `loader`
+//! module. `loader::Handle` is an object-safe trait which abstracts both file
+//! loading and file watching. `Handle` is dynamically configured with a set of
+//! directory entries which should be scanned and watched. `Handle` then
+//! asynchronously pushes file changes. Directory entries are configured in
+//! free-form via list of globs, it's up to the `Handle` to interpret the globs
+//! in any specific way.
+//!
+//! A simple `WalkdirLoaderHandle` is provided, which doesn't implement watching
+//! and just scans the directory using walkdir.
+//!
+//! VFS stores a flat list of files. `FileSet` can partition this list of files
+//! into disjoint sets of files. Traversal-like operations (including getting
+//! the neighbor file by the relative path) are handled by the `FileSet`.
+//! `FileSet`s are also pushed to salsa and cause it to re-check `mod foo;`
+//! declarations when files are created or deleted.
+//!
+//! `file_set::FileSet` and `loader::Entry` play similar, but different roles.
+//! Both specify the "set of paths/files", one is geared towards file watching,
+//! the other towards salsa changes. In particular, single `file_set::FileSet`
+//! may correspond to several `loader::Entry`. For example, a crate from
+//! crates.io which uses code generation would have two `Entries` -- for sources
+//! in `~/.cargo`, and for generated code in `./target/debug/build`. It will
+//! have a single `FileSet` which unions the two sources.
+mod vfs_path;
+mod path_interner;
+pub mod file_set;
+pub mod loader;
+pub mod walkdir_loader;
+
+use std::{fmt, mem};
+
+use crate::path_interner::PathInterner;
+
+pub use crate::vfs_path::VfsPath;
+pub use paths::{AbsPath, AbsPathBuf};
+
+#[derive(Copy, Clone, Debug, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct FileId(pub u32);
+
+#[derive(Default)]
+pub struct Vfs {
+    interner: PathInterner,
+    data: Vec<Option<Vec<u8>>>,
+    changes: Vec<ChangedFile>,
+}
+
+pub struct ChangedFile {
+    pub file_id: FileId,
+    pub change_kind: ChangeKind,
+}
+
+impl ChangedFile {
+    pub fn exists(&self) -> bool {
+        self.change_kind != ChangeKind::Delete
+    }
+    pub fn is_created_or_deleted(&self) -> bool {
+        matches!(self.change_kind, ChangeKind::Create | ChangeKind::Delete)
+    }
+}
+
+#[derive(Eq, PartialEq)]
+pub enum ChangeKind {
+    Create,
+    Modify,
+    Delete,
+}
+
+impl Vfs {
+    pub fn len(&self) -> usize {
+        self.data.len()
+    }
+    pub fn file_id(&self, path: &VfsPath) -> Option<FileId> {
+        self.interner.get(path).filter(|&it| self.get(it).is_some())
+    }
+    pub fn file_path(&self, file_id: FileId) -> VfsPath {
+        self.interner.lookup(file_id).clone()
+    }
+    pub fn file_contents(&self, file_id: FileId) -> &[u8] {
+        self.get(file_id).as_deref().unwrap()
+    }
+    pub fn iter(&self) -> impl Iterator<Item = (FileId, VfsPath)> + '_ {
+        (0..self.data.len())
+            .map(|it| FileId(it as u32))
+            .filter(move |&file_id| self.get(file_id).is_some())
+            .map(move |file_id| {
+                let path = self.interner.lookup(file_id).clone();
+                (file_id, path)
+            })
+    }
+    pub fn set_file_contents(&mut self, path: VfsPath, contents: Option<Vec<u8>>) {
+        let file_id = self.alloc_file_id(path);
+        let change_kind = match (&self.get(file_id), &contents) {
+            (None, None) => return,
+            (None, Some(_)) => ChangeKind::Create,
+            (Some(_), None) => ChangeKind::Delete,
+            (Some(old), Some(new)) if old == new => return,
+            (Some(_), Some(_)) => ChangeKind::Modify,
+        };
+
+        *self.get_mut(file_id) = contents;
+        self.changes.push(ChangedFile { file_id, change_kind })
+    }
+    pub fn has_changes(&self) -> bool {
+        !self.changes.is_empty()
+    }
+    pub fn take_changes(&mut self) -> Vec<ChangedFile> {
+        mem::take(&mut self.changes)
+    }
+    fn alloc_file_id(&mut self, path: VfsPath) -> FileId {
+        let file_id = self.interner.intern(path);
+        let idx = file_id.0 as usize;
+        let len = self.data.len().max(idx + 1);
+        self.data.resize_with(len, || None);
+        file_id
+    }
+    fn get(&self, file_id: FileId) -> &Option<Vec<u8>> {
+        &self.data[file_id.0 as usize]
+    }
+    fn get_mut(&mut self, file_id: FileId) -> &mut Option<Vec<u8>> {
+        &mut self.data[file_id.0 as usize]
+    }
+}
+
+impl fmt::Debug for Vfs {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Vfs").field("n_files", &self.data.len()).finish()
+    }
+}
diff --git a/crates/vfs/src/loader.rs b/crates/vfs/src/loader.rs
new file mode 100644
index 000000000..5a0ca68f3
--- /dev/null
+++ b/crates/vfs/src/loader.rs
@@ -0,0 +1,69 @@
+//! Object safe interface for file watching and reading.
+use std::fmt;
+
+use paths::AbsPathBuf;
+
+pub enum Entry {
+    Files(Vec<AbsPathBuf>),
+    Directory { path: AbsPathBuf, globs: Vec<String> },
+}
+
+pub struct Config {
+    pub load: Vec<Entry>,
+    pub watch: Vec<usize>,
+}
+
+pub enum Message {
+    DidSwitchConfig { n_entries: usize },
+    DidLoadAllEntries,
+    Loaded { files: Vec<(AbsPathBuf, Option<Vec<u8>>)> },
+}
+
+pub type Sender = Box<dyn Fn(Message) + Send>;
+
+pub trait Handle: fmt::Debug {
+    fn spawn(sender: Sender) -> Self
+    where
+        Self: Sized;
+    fn set_config(&mut self, config: Config);
+    fn invalidate(&mut self, path: AbsPathBuf);
+    fn load_sync(&mut self, path: &AbsPathBuf) -> Option<Vec<u8>>;
+}
+
+impl Entry {
+    pub fn rs_files_recursively(base: AbsPathBuf) -> Entry {
+        Entry::Directory { path: base, globs: globs(&["*.rs"]) }
+    }
+    pub fn local_cargo_package(base: AbsPathBuf) -> Entry {
+        Entry::Directory { path: base, globs: globs(&["*.rs", "!/target/"]) }
+    }
+    pub fn cargo_package_dependency(base: AbsPathBuf) -> Entry {
+        Entry::Directory {
+            path: base,
+            globs: globs(&["*.rs", "!/tests/", "!/examples/", "!/benches/"]),
+        }
+    }
+}
+
+fn globs(globs: &[&str]) -> Vec<String> {
+    globs.iter().map(|it| it.to_string()).collect()
+}
+
+impl fmt::Debug for Message {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Message::Loaded { files } => {
+                f.debug_struct("Loaded").field("n_files", &files.len()).finish()
+            }
+            Message::DidSwitchConfig { n_entries } => {
+                f.debug_struct("DidSwitchConfig").field("n_entries", n_entries).finish()
+            }
+            Message::DidLoadAllEntries => f.debug_struct("DidLoadAllEntries").finish(),
+        }
+    }
+}
+
+#[test]
+fn handle_is_object_safe() {
+    fn _assert(_: &dyn Handle) {}
+}
diff --git a/crates/vfs/src/path_interner.rs b/crates/vfs/src/path_interner.rs
new file mode 100644
index 000000000..4f70d61e8
--- /dev/null
+++ b/crates/vfs/src/path_interner.rs
@@ -0,0 +1,31 @@
+//! Maps paths to compact integer ids. We don't care about clearings paths which
+//! no longer exist -- the assumption is total size of paths we ever look at is
+//! not too big.
+use rustc_hash::FxHashMap;
+
+use crate::{FileId, VfsPath};
+
+#[derive(Default)]
+pub(crate) struct PathInterner {
+    map: FxHashMap<VfsPath, FileId>,
+    vec: Vec<VfsPath>,
+}
+
+impl PathInterner {
+    pub(crate) fn get(&self, path: &VfsPath) -> Option<FileId> {
+        self.map.get(path).copied()
+    }
+    pub(crate) fn intern(&mut self, path: VfsPath) -> FileId {
+        if let Some(id) = self.get(&path) {
+            return id;
+        }
+        let id = FileId(self.vec.len() as u32);
+        self.map.insert(path.clone(), id);
+        self.vec.push(path);
+        id
+    }
+
+    pub(crate) fn lookup(&self, id: FileId) -> &VfsPath {
+        &self.vec[id.0 as usize]
+    }
+}
diff --git a/crates/vfs/src/vfs_path.rs b/crates/vfs/src/vfs_path.rs
new file mode 100644
index 000000000..de5dc0bf3
--- /dev/null
+++ b/crates/vfs/src/vfs_path.rs
@@ -0,0 +1,49 @@
+//! Abstract-ish representation of paths for VFS.
+use std::fmt;
+
+use paths::{AbsPath, AbsPathBuf};
+
+/// Long-term, we want to support files which do not reside in the file-system,
+/// so we treat VfsPaths as opaque identifiers.
+#[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct VfsPath(VfsPathRepr);
+
+impl VfsPath {
+    pub fn as_path(&self) -> Option<&AbsPath> {
+        match &self.0 {
+            VfsPathRepr::PathBuf(it) => Some(it.as_path()),
+        }
+    }
+    pub fn join(&self, path: &str) -> VfsPath {
+        match &self.0 {
+            VfsPathRepr::PathBuf(it) => {
+                let res = it.join(path).normalize();
+                VfsPath(VfsPathRepr::PathBuf(res))
+            }
+        }
+    }
+    pub fn pop(&mut self) -> bool {
+        match &mut self.0 {
+            VfsPathRepr::PathBuf(it) => it.pop(),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+enum VfsPathRepr {
+    PathBuf(AbsPathBuf),
+}
+
+impl From<AbsPathBuf> for VfsPath {
+    fn from(v: AbsPathBuf) -> Self {
+        VfsPath(VfsPathRepr::PathBuf(v))
+    }
+}
+
+impl fmt::Display for VfsPath {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match &self.0 {
+            VfsPathRepr::PathBuf(it) => fmt::Display::fmt(&it.display(), f),
+        }
+    }
+}
diff --git a/crates/vfs/src/walkdir_loader.rs b/crates/vfs/src/walkdir_loader.rs
new file mode 100644
index 000000000..13e59e3f3
--- /dev/null
+++ b/crates/vfs/src/walkdir_loader.rs
@@ -0,0 +1,108 @@
+//! A walkdir-based implementation of `loader::Handle`, which doesn't try to
+//! watch files.
+use std::convert::TryFrom;
+
+use globset::{Glob, GlobSetBuilder};
+use paths::{AbsPath, AbsPathBuf};
+use walkdir::WalkDir;
+
+use crate::loader;
+
+#[derive(Debug)]
+pub struct WalkdirLoaderHandle {
+    // Relative order of fields below is significant.
+    sender: crossbeam_channel::Sender<Message>,
+    _thread: jod_thread::JoinHandle,
+}
+
+enum Message {
+    Config(loader::Config),
+    Invalidate(AbsPathBuf),
+}
+
+impl loader::Handle for WalkdirLoaderHandle {
+    fn spawn(sender: loader::Sender) -> WalkdirLoaderHandle {
+        let actor = WalkdirLoaderActor { sender };
+        let (sender, receiver) = crossbeam_channel::unbounded::<Message>();
+        let thread = jod_thread::spawn(move || actor.run(receiver));
+        WalkdirLoaderHandle { sender, _thread: thread }
+    }
+    fn set_config(&mut self, config: loader::Config) {
+        self.sender.send(Message::Config(config)).unwrap()
+    }
+    fn invalidate(&mut self, path: AbsPathBuf) {
+        self.sender.send(Message::Invalidate(path)).unwrap();
+    }
+    fn load_sync(&mut self, path: &AbsPathBuf) -> Option<Vec<u8>> {
+        read(path)
+    }
+}
+
+struct WalkdirLoaderActor {
+    sender: loader::Sender,
+}
+
+impl WalkdirLoaderActor {
+    fn run(mut self, receiver: crossbeam_channel::Receiver<Message>) {
+        for msg in receiver {
+            match msg {
+                Message::Config(config) => {
+                    self.send(loader::Message::DidSwitchConfig { n_entries: config.load.len() });
+                    for entry in config.load.into_iter() {
+                        let files = self.load_entry(entry);
+                        self.send(loader::Message::Loaded { files });
+                    }
+                    drop(config.watch);
+                    self.send(loader::Message::DidLoadAllEntries);
+                }
+                Message::Invalidate(path) => {
+                    let contents = read(path.as_path());
+                    let files = vec![(path, contents)];
+                    self.send(loader::Message::Loaded { files });
+                }
+            }
+        }
+    }
+    fn load_entry(&mut self, entry: loader::Entry) -> Vec<(AbsPathBuf, Option<Vec<u8>>)> {
+        match entry {
+            loader::Entry::Files(files) => files
+                .into_iter()
+                .map(|file| {
+                    let contents = read(file.as_path());
+                    (file, contents)
+                })
+                .collect::<Vec<_>>(),
+            loader::Entry::Directory { path, globs } => {
+                let globset = {
+                    let mut builder = GlobSetBuilder::new();
+                    for glob in &globs {
+                        builder.add(Glob::new(glob).unwrap());
+                    }
+                    builder.build().unwrap()
+                };
+
+                let files = WalkDir::new(path)
+                    .into_iter()
+                    .filter_map(|it| it.ok())
+                    .filter(|it| it.file_type().is_file())
+                    .map(|it| it.into_path())
+                    .map(|it| AbsPathBuf::try_from(it).unwrap())
+                    .filter(|it| globset.is_match(&it));
+
+                files
+                    .map(|file| {
+                        let contents = read(file.as_path());
+                        (file, contents)
+                    })
+                    .collect()
+            }
+        }
+    }
+    fn send(&mut self, msg: loader::Message) {
+        (self.sender)(msg)
+    }
+}
+
+fn read(path: &AbsPath) -> Option<Vec<u8>> {
+    std::fs::read(path).ok()
+}