45 files changed, 685 insertions, 247 deletions

diff --git a/crates/assists/src/ast_transform.rs b/crates/assists/src/ast_transform.rs
index 4c41c16d8..5216862ba 100644
--- a/crates/assists/src/ast_transform.rs
+++ b/crates/assists/src/ast_transform.rs
@@ -7,6 +7,17 @@ use syntax::{
     ast::{self, AstNode},
 };
 
+pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
+    SyntaxRewriter::from_fn(|element| match element {
+        syntax::SyntaxElement::Node(n) => {
+            let replacement = transformer.get_substitution(&n)?;
+            Some(replacement.into())
+        }
+        _ => None,
+    })
+    .rewrite_ast(&node)
+}
+
 pub trait AstTransform<'a> {
     fn get_substitution(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode>;
 
@@ -107,10 +118,7 @@ impl<'a> SubstituteTypeParams<'a> {
             ast::Type::PathType(path_type) => path_type.path()?,
             _ => 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)?;
+        let resolution = self.source_scope.speculative_resolve(&path)?;
         match resolution {
             hir::PathResolution::TypeParam(tp) => Some(self.substs.get(&tp)?.syntax().clone()),
             _ => None,
@@ -146,10 +154,7 @@ impl<'a> QualifyPaths<'a> {
             // don't try to qualify `Fn(Foo) -> Bar` paths, they are in prelude anyway
             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?)?;
+        let resolution = self.source_scope.speculative_resolve(&p)?;
         match resolution {
             PathResolution::Def(def) => {
                 let found_path = from.find_use_path(self.source_scope.db.upcast(), def)?;
@@ -175,17 +180,6 @@ impl<'a> QualifyPaths<'a> {
     }
 }
 
-pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
-    SyntaxRewriter::from_fn(|element| match element {
-        syntax::SyntaxElement::Node(n) => {
-            let replacement = transformer.get_substitution(&n)?;
-            Some(replacement.into())
-        }
-        _ => None,
-    })
-    .rewrite_ast(&node)
-}
-
 impl<'a> AstTransform<'a> for QualifyPaths<'a> {
     fn get_substitution(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
         self.get_substitution_inner(node).or_else(|| self.previous.get_substitution(node))
diff --git a/crates/assists/src/handlers/add_missing_impl_members.rs b/crates/assists/src/handlers/add_missing_impl_members.rs
index 81b61ebf8..83a2ada9a 100644
--- a/crates/assists/src/handlers/add_missing_impl_members.rs
+++ b/crates/assists/src/handlers/add_missing_impl_members.rs
@@ -48,7 +48,6 @@ enum AddMissingImplMembersMode {
 //     fn foo(&self) -> u32 {
 //         ${0:todo!()}
 //     }
-//
 // }
 // ```
 pub(crate) fn add_missing_impl_members(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
@@ -89,8 +88,8 @@ pub(crate) fn add_missing_impl_members(acc: &mut Assists, ctx: &AssistContext) -
 // impl Trait for () {
 //     Type X = ();
 //     fn foo(&self) {}
-//     $0fn bar(&self) {}
 //
+//     $0fn bar(&self) {}
 // }
 // ```
 pub(crate) fn add_missing_default_members(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
@@ -240,15 +239,18 @@ struct S;
 
 impl Foo for S {
     fn bar(&self) {}
+
     $0type Output;
+
     const CONST: usize = 42;
+
     fn foo(&self) {
         todo!()
     }
+
     fn baz(&self) {
         todo!()
     }
-
 }"#,
         );
     }
@@ -281,10 +283,10 @@ struct S;
 
 impl Foo for S {
     fn bar(&self) {}
+
     fn foo(&self) {
         ${0:todo!()}
     }
-
 }"#,
         );
     }
@@ -599,6 +601,7 @@ trait Foo {
 struct S;
 impl Foo for S {
     $0type Output;
+
     fn foo(&self) {
         todo!()
     }
@@ -708,4 +711,56 @@ impl Tr for () {
 }"#,
         )
     }
+
+    #[test]
+    fn test_whitespace_fixup_preserves_bad_tokens() {
+        check_assist(
+            add_missing_impl_members,
+            r#"
+trait Tr {
+    fn foo();
+}
+
+impl Tr for ()<|> {
+    +++
+}"#,
+            r#"
+trait Tr {
+    fn foo();
+}
+
+impl Tr for () {
+    fn foo() {
+        ${0:todo!()}
+    }
+    +++
+}"#,
+        )
+    }
+
+    #[test]
+    fn test_whitespace_fixup_preserves_comments() {
+        check_assist(
+            add_missing_impl_members,
+            r#"
+trait Tr {
+    fn foo();
+}
+
+impl Tr for ()<|> {
+    // very important
+}"#,
+            r#"
+trait Tr {
+    fn foo();
+}
+
+impl Tr for () {
+    fn foo() {
+        ${0:todo!()}
+    }
+    // very important
+}"#,
+        )
+    }
 }
diff --git a/crates/assists/src/handlers/auto_import.rs b/crates/assists/src/handlers/auto_import.rs
index cce789972..b9ec3f10b 100644
--- a/crates/assists/src/handlers/auto_import.rs
+++ b/crates/assists/src/handlers/auto_import.rs
@@ -53,7 +53,7 @@ pub(crate) fn auto_import(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
             |builder| {
                 insert_use_statement(
                     &auto_import_assets.syntax_under_caret,
-                    &import,
+                    &import.to_string(),
                     ctx,
                     builder.text_edit_builder(),
                 );
diff --git a/crates/assists/src/handlers/expand_glob_import.rs b/crates/assists/src/handlers/expand_glob_import.rs
index f690ec343..81d0af2f3 100644
--- a/crates/assists/src/handlers/expand_glob_import.rs
+++ b/crates/assists/src/handlers/expand_glob_import.rs
@@ -1,3 +1,4 @@
+use either::Either;
 use hir::{AssocItem, MacroDef, ModuleDef, Name, PathResolution, ScopeDef, SemanticsScope};
 use ide_db::{
     defs::{classify_name_ref, Definition, NameRefClass},
@@ -10,8 +11,6 @@ use crate::{
     AssistId, AssistKind,
 };
 
-use either::Either;
-
 // Assist: expand_glob_import
 //
 // Expands glob imports.
@@ -40,11 +39,15 @@ use either::Either;
 pub(crate) fn expand_glob_import(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let star = ctx.find_token_at_offset(T![*])?;
     let mod_path = find_mod_path(&star)?;
+    let module = match ctx.sema.resolve_path(&mod_path)? {
+        PathResolution::Def(ModuleDef::Module(it)) => it,
+        _ => return None,
+    };
 
     let source_file = ctx.source_file();
     let scope = ctx.sema.scope_at_offset(source_file.syntax(), ctx.offset());
 
-    let defs_in_mod = find_defs_in_mod(ctx, scope, &mod_path)?;
+    let defs_in_mod = find_defs_in_mod(ctx, scope, module)?;
     let name_refs_in_source_file =
         source_file.syntax().descendants().filter_map(ast::NameRef::cast).collect();
     let used_names = find_used_names(ctx, defs_in_mod, name_refs_in_source_file);
@@ -82,17 +85,8 @@ impl Def {
 fn find_defs_in_mod(
     ctx: &AssistContext,
     from: SemanticsScope<'_>,
-    path: &ast::Path,
+    module: hir::Module,
 ) -> Option<Vec<Def>> {
-    let hir_path = ctx.sema.lower_path(&path)?;
-    let module = if let Some(PathResolution::Def(ModuleDef::Module(module))) =
-        from.resolve_hir_path_qualifier(&hir_path)
-    {
-        module
-    } else {
-        return None;
-    };
-
     let module_scope = module.scope(ctx.db(), from.module());
 
     let mut defs = vec![];
diff --git a/crates/assists/src/handlers/extract_struct_from_enum_variant.rs b/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
index 4bcdae7ba..d62e06b4a 100644
--- a/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
+++ b/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
@@ -106,7 +106,12 @@ fn insert_import(
     if let Some(mut mod_path) = mod_path {
         mod_path.segments.pop();
         mod_path.segments.push(variant_hir_name.clone());
-        insert_use_statement(path.syntax(), &mod_path, ctx, builder.text_edit_builder());
+        insert_use_statement(
+            path.syntax(),
+            &mod_path.to_string(),
+            ctx,
+            builder.text_edit_builder(),
+        );
     }
     Some(())
 }
diff --git a/crates/assists/src/handlers/replace_qualified_name_with_use.rs b/crates/assists/src/handlers/replace_qualified_name_with_use.rs
index 011bf1106..470e5f8ff 100644
--- a/crates/assists/src/handlers/replace_qualified_name_with_use.rs
+++ b/crates/assists/src/handlers/replace_qualified_name_with_use.rs
@@ -1,5 +1,5 @@
-use hir;
-use syntax::{algo::SyntaxRewriter, ast, match_ast, AstNode, SmolStr, SyntaxNode};
+use syntax::{algo::SyntaxRewriter, ast, match_ast, AstNode, SyntaxNode, TextRange};
+use test_utils::mark;
 
 use crate::{
     utils::{find_insert_use_container, insert_use_statement},
@@ -28,12 +28,19 @@ pub(crate) fn replace_qualified_name_with_use(
     if path.syntax().ancestors().find_map(ast::Use::cast).is_some() {
         return None;
     }
-
-    let hir_path = ctx.sema.lower_path(&path)?;
-    let segments = collect_hir_path_segments(&hir_path)?;
-    if segments.len() < 2 {
+    if path.qualifier().is_none() {
+        mark::hit!(dont_import_trivial_paths);
         return None;
     }
+    let path_to_import = path.to_string().clone();
+    let path_to_import = match path.segment()?.generic_arg_list() {
+        Some(generic_args) => {
+            let generic_args_start =
+                generic_args.syntax().text_range().start() - path.syntax().text_range().start();
+            &path_to_import[TextRange::up_to(generic_args_start)]
+        }
+        None => path_to_import.as_str(),
+    };
 
     let target = path.syntax().text_range();
     acc.add(
@@ -41,12 +48,16 @@ pub(crate) fn replace_qualified_name_with_use(
         "Replace qualified path 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());
+            insert_use_statement(
+                path.syntax(),
+                &path_to_import.to_string(),
+                ctx,
+                builder.text_edit_builder(),
+            );
 
             // 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).
@@ -58,26 +69,6 @@ pub(crate) fn replace_qualified_name_with_use(
     )
 }
 
-fn collect_hir_path_segments(path: &hir::Path) -> Option<Vec<SmolStr>> {
-    let mut ps = Vec::<SmolStr>::with_capacity(10);
-    match path.kind() {
-        hir::PathKind::Abs => ps.push("".into()),
-        hir::PathKind::Crate => ps.push("crate".into()),
-        hir::PathKind::Plain => {}
-        hir::PathKind::Super(0) => ps.push("self".into()),
-        hir::PathKind::Super(lvl) => {
-            let mut chain = "super".to_string();
-            for _ in 0..*lvl {
-                chain += "::super";
-            }
-            ps.push(chain.into());
-        }
-        hir::PathKind::DollarCrate(_) => return None,
-    }
-    ps.extend(path.segments().iter().map(|it| it.name.to_string().into()));
-    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() {
@@ -467,7 +458,8 @@ impl Debug for Foo {
     }
 
     #[test]
-    fn test_replace_not_applicable_one_segment() {
+    fn dont_import_trivial_paths() {
+        mark::check!(dont_import_trivial_paths);
         check_assist_not_applicable(
             replace_qualified_name_with_use,
             r"
diff --git a/crates/assists/src/lib.rs b/crates/assists/src/lib.rs
index ae90d68a3..c589b08dc 100644
--- a/crates/assists/src/lib.rs
+++ b/crates/assists/src/lib.rs
@@ -66,13 +66,13 @@ pub struct GroupLabel(pub String);
 
 #[derive(Debug, Clone)]
 pub struct Assist {
-    id: AssistId,
+    pub id: AssistId,
     /// Short description of the assist, as shown in the UI.
     label: String,
-    group: Option<GroupLabel>,
+    pub group: Option<GroupLabel>,
     /// Target ranges are used to sort assists: the smaller the target range,
     /// the more specific assist is, and so it should be sorted first.
-    target: TextRange,
+    pub target: TextRange,
 }
 
 #[derive(Debug, Clone)]
@@ -82,6 +82,11 @@ pub struct ResolvedAssist {
 }
 
 impl Assist {
+    fn new(id: AssistId, label: String, group: Option<GroupLabel>, target: TextRange) -> Assist {
+        assert!(label.starts_with(char::is_uppercase));
+        Assist { id, label, group, target }
+    }
+
     /// Return all the assists applicable at the given position.
     ///
     /// Assists are returned in the "unresolved" state, that is only labels are
@@ -114,30 +119,8 @@ impl Assist {
         acc.finish_resolved()
     }
 
-    pub(crate) fn new(
-        id: AssistId,
-        label: String,
-        group: Option<GroupLabel>,
-        target: TextRange,
-    ) -> Assist {
-        assert!(label.starts_with(|c: char| c.is_uppercase()));
-        Assist { id, label, group, target }
-    }
-
-    pub fn id(&self) -> AssistId {
-        self.id
-    }
-
-    pub fn label(&self) -> String {
-        self.label.clone()
-    }
-
-    pub fn group(&self) -> Option<GroupLabel> {
-        self.group.clone()
-    }
-
-    pub fn target(&self) -> TextRange {
-        self.target
+    pub fn label(&self) -> &str {
+        self.label.as_str()
     }
 }
 
diff --git a/crates/assists/src/tests/generated.rs b/crates/assists/src/tests/generated.rs
index d16e6fb0a..173567003 100644
--- a/crates/assists/src/tests/generated.rs
+++ b/crates/assists/src/tests/generated.rs
@@ -82,8 +82,8 @@ trait Trait {
 impl Trait for () {
     Type X = ();
     fn foo(&self) {}
-    $0fn bar(&self) {}
 
+    $0fn bar(&self) {}
 }
 "#####,
     )
@@ -115,7 +115,6 @@ impl Trait<u32> for () {
     fn foo(&self) -> u32 {
         ${0:todo!()}
     }
-
 }
 "#####,
     )
diff --git a/crates/assists/src/utils/insert_use.rs b/crates/assists/src/utils/insert_use.rs
index 50a62ee82..49096a67c 100644
--- a/crates/assists/src/utils/insert_use.rs
+++ b/crates/assists/src/utils/insert_use.rs
@@ -5,7 +5,6 @@
 use std::iter::successors;
 
 use either::Either;
-use hir::{self, ModPath};
 use syntax::{
     ast::{self, NameOwner, VisibilityOwner},
     AstNode, AstToken, Direction, SmolStr,
@@ -35,11 +34,11 @@ pub(crate) fn find_insert_use_container(
 pub(crate) fn insert_use_statement(
     // Ideally the position of the cursor, used to
     position: &SyntaxNode,
-    path_to_import: &ModPath,
+    path_to_import: &str,
     ctx: &AssistContext,
     builder: &mut TextEditBuilder,
 ) {
-    let target = path_to_import.to_string().split("::").map(SmolStr::new).collect::<Vec<_>>();
+    let target = path_to_import.split("::").map(SmolStr::new).collect::<Vec<_>>();
     let container = find_insert_use_container(position, ctx);
 
     if let Some(container) = container {
diff --git a/crates/hir/src/code_model.rs b/crates/hir/src/code_model.rs
index 5dc3ae3b1..c442654dd 100644
--- a/crates/hir/src/code_model.rs
+++ b/crates/hir/src/code_model.rs
@@ -12,6 +12,7 @@ use hir_def::{
     docs::Documentation,
     expr::{BindingAnnotation, Pat, PatId},
     import_map,
+    path::ModPath,
     per_ns::PerNs,
     resolver::{HasResolver, Resolver},
     src::HasSource as _,
@@ -344,11 +345,7 @@ impl Module {
 
     /// Finds a path that can be used to refer to the given item from within
     /// this module, if possible.
-    pub fn find_use_path(
-        self,
-        db: &dyn DefDatabase,
-        item: impl Into<ItemInNs>,
-    ) -> Option<hir_def::path::ModPath> {
+    pub fn find_use_path(self, db: &dyn DefDatabase, item: impl Into<ItemInNs>) -> Option<ModPath> {
         hir_def::find_path::find_path(db, item.into(), self.into())
     }
 }
@@ -1126,7 +1123,7 @@ impl ImplDef {
             .value
             .attrs()
             .filter_map(|it| {
-                let path = hir_def::path::ModPath::from_src(it.path()?, &hygenic)?;
+                let path = ModPath::from_src(it.path()?, &hygenic)?;
                 if path.as_ident()?.to_string() == "derive" {
                     Some(it)
                 } else {
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 4ae2bd085..8961ba8fd 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -48,7 +48,7 @@ pub use hir_def::{
     builtin_type::BuiltinType,
     docs::Documentation,
     nameres::ModuleSource,
-    path::{ModPath, Path, PathKind},
+    path::ModPath,
     type_ref::{Mutability, TypeRef},
 };
 pub use hir_expand::{
@@ -60,4 +60,7 @@ pub use hir_ty::display::HirDisplay;
 // These are negative re-exports: pub using these names is forbidden, they
 // should remain private to hir internals.
 #[allow(unused)]
-use hir_expand::hygiene::Hygiene;
+use {
+    hir_def::path::{Path, PathKind},
+    hir_expand::hygiene::Hygiene,
+};
diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index d8beac98a..c693176fa 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -6,7 +6,7 @@ use std::{cell::RefCell, fmt, iter::successors};
 
 use base_db::{FileId, FileRange};
 use hir_def::{
-    resolver::{self, HasResolver, Resolver},
+    resolver::{self, HasResolver, Resolver, TypeNs},
     AsMacroCall, FunctionId, TraitId, VariantId,
 };
 use hir_expand::{hygiene::Hygiene, name::AsName, ExpansionInfo};
@@ -22,12 +22,11 @@ use crate::{
     db::HirDatabase,
     diagnostics::Diagnostic,
     semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
-    source_analyzer::{resolve_hir_path, resolve_hir_path_qualifier, SourceAnalyzer},
+    source_analyzer::{resolve_hir_path, SourceAnalyzer},
     AssocItem, Callable, Crate, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef,
     Module, ModuleDef, Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, TypeRef,
     VariantDef,
 };
-use resolver::TypeNs;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum PathResolution {
@@ -112,14 +111,13 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
     pub fn expand(&self, macro_call: &ast::MacroCall) -> Option<SyntaxNode> {
         self.imp.expand(macro_call)
     }
-
-    pub fn expand_hypothetical(
+    pub fn speculative_expand(
         &self,
         actual_macro_call: &ast::MacroCall,
         hypothetical_args: &ast::TokenTree,
         token_to_map: SyntaxToken,
     ) -> Option<(SyntaxNode, SyntaxToken)> {
-        self.imp.expand_hypothetical(actual_macro_call, hypothetical_args, token_to_map)
+        self.imp.speculative_expand(actual_macro_call, hypothetical_args, token_to_map)
     }
 
     pub fn descend_into_macros(&self, token: SyntaxToken) -> SyntaxToken {
@@ -229,10 +227,6 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         self.imp.resolve_variant(record_lit).map(VariantDef::from)
     }
 
-    pub fn lower_path(&self, path: &ast::Path) -> Option<Path> {
-        self.imp.lower_path(path)
-    }
-
     pub fn resolve_bind_pat_to_const(&self, pat: &ast::IdentPat) -> Option<ModuleDef> {
         self.imp.resolve_bind_pat_to_const(pat)
     }
@@ -311,7 +305,7 @@ impl<'db> SemanticsImpl<'db> {
         Some(node)
     }
 
-    fn expand_hypothetical(
+    fn speculative_expand(
         &self,
         actual_macro_call: &ast::MacroCall,
         hypothetical_args: &ast::TokenTree,
@@ -468,11 +462,6 @@ impl<'db> SemanticsImpl<'db> {
         self.analyze(record_lit.syntax()).resolve_variant(self.db, record_lit)
     }
 
-    fn lower_path(&self, path: &ast::Path) -> Option<Path> {
-        let src = self.find_file(path.syntax().clone());
-        Path::from_src(path.clone(), &Hygiene::new(self.db.upcast(), src.file_id.into()))
-    }
-
     fn resolve_bind_pat_to_const(&self, pat: &ast::IdentPat) -> Option<ModuleDef> {
         self.analyze(pat.syntax()).resolve_bind_pat_to_const(self.db, pat)
     }
@@ -756,31 +745,10 @@ impl<'a> SemanticsScope<'a> {
 
     /// Resolve a path as-if it was written at the given scope. This is
     /// necessary a heuristic, as it doesn't take hygiene into account.
-    pub fn resolve_hypothetical(&self, path: &ast::Path) -> Option<PathResolution> {
+    pub fn speculative_resolve(&self, path: &ast::Path) -> Option<PathResolution> {
         let hygiene = Hygiene::new(self.db.upcast(), self.file_id);
         let path = Path::from_src(path.clone(), &hygiene)?;
-        self.resolve_hir_path(&path)
-    }
-
-    pub fn resolve_hir_path(&self, path: &Path) -> Option<PathResolution> {
-        resolve_hir_path(self.db, &self.resolver, path)
-    }
-
-    /// Resolves a path where we know it is a qualifier of another path.
-    ///
-    /// For example, if we have:
-    /// ```
-    /// mod my {
-    ///     pub mod foo {
-    ///         struct Bar;
-    ///     }
-    ///
-    ///     pub fn foo() {}
-    /// }
-    /// ```
-    /// then we know that `foo` in `my::foo::Bar` refers to the module, not the function.
-    pub fn resolve_hir_path_qualifier(&self, path: &Path) -> Option<PathResolution> {
-        resolve_hir_path_qualifier(self.db, &self.resolver, path)
+        resolve_hir_path(self.db, &self.resolver, &path)
     }
 }
 
diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
index 8750584f9..1d13c4f1d 100644
--- a/crates/hir/src/source_analyzer.rs
+++ b/crates/hir/src/source_analyzer.rs
@@ -13,6 +13,7 @@ use hir_def::{
         Body, BodySourceMap,
     },
     expr::{ExprId, Pat, PatId},
+    path::{ModPath, Path, PathKind},
     resolver::{resolver_for_scope, Resolver, TypeNs, ValueNs},
     AsMacroCall, DefWithBodyId, FieldId, FunctionId, LocalFieldId, VariantId,
 };
@@ -28,8 +29,7 @@ use syntax::{
 
 use crate::{
     db::HirDatabase, semantics::PathResolution, Adt, Const, EnumVariant, Field, Function, Local,
-    MacroDef, ModPath, ModuleDef, Path, PathKind, Static, Struct, Trait, Type, TypeAlias,
-    TypeParam,
+    MacroDef, ModuleDef, Static, Struct, Trait, Type, TypeAlias, TypeParam,
 };
 use base_db::CrateId;
 
@@ -508,7 +508,7 @@ pub(crate) fn resolve_hir_path(
 /// }
 /// ```
 /// then we know that `foo` in `my::foo::Bar` refers to the module, not the function.
-pub(crate) fn resolve_hir_path_qualifier(
+fn resolve_hir_path_qualifier(
     db: &dyn HirDatabase,
     resolver: &Resolver,
     path: &Path,
diff --git a/crates/hir_def/src/path.rs b/crates/hir_def/src/path.rs
index 74d26f08b..99395667d 100644
--- a/crates/hir_def/src/path.rs
+++ b/crates/hir_def/src/path.rs
@@ -154,12 +154,6 @@ pub enum GenericArg {
 
 impl Path {
     /// Converts an `ast::Path` to `Path`. Works with use trees.
-    #[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())
-    }
-
-    /// Converts an `ast::Path` to `Path`. Works with use trees.
     /// It correctly handles `$crate` based path from macro call.
     pub fn from_src(path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
         lower::lower_path(path, hygiene)
diff --git a/crates/hir_ty/Cargo.toml b/crates/hir_ty/Cargo.toml
index 83b5013a9..a319b0ce8 100644
--- a/crates/hir_ty/Cargo.toml
+++ b/crates/hir_ty/Cargo.toml
@@ -16,9 +16,9 @@ ena = "0.14.0"
 log = "0.4.8"
 rustc-hash = "1.1.0"
 scoped-tls = "1"
-chalk-solve = { version = "0.21.0" }
-chalk-ir = { version = "0.21.0" }
-chalk-recursive = { version = "0.21.0" }
+chalk-solve = { version = "0.23.0" }
+chalk-ir = { version = "0.23.0" }
+chalk-recursive = { version = "0.23.0" }
 
 stdx = { path = "../stdx" }
 hir_def = { path = "../hir_def" }
diff --git a/crates/hir_ty/src/diagnostics/expr.rs b/crates/hir_ty/src/diagnostics/expr.rs
index fb76e2e4e..278a4b947 100644
--- a/crates/hir_ty/src/diagnostics/expr.rs
+++ b/crates/hir_ty/src/diagnostics/expr.rs
@@ -223,10 +223,10 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             db.body_with_source_map(self.owner.into());
 
         let match_expr_ty = match infer.type_of_expr.get(match_expr) {
-            Some(ty) => ty,
             // If we can't resolve the type of the match expression
             // we cannot perform exhaustiveness checks.
-            None => return,
+            None | Some(Ty::Unknown) => return,
+            Some(ty) => ty,
         };
 
         let cx = MatchCheckCtx { match_expr, body, infer: infer.clone(), db };
diff --git a/crates/hir_ty/src/diagnostics/match_check.rs b/crates/hir_ty/src/diagnostics/match_check.rs
index 7f007f1d6..5bd03f2ac 100644
--- a/crates/hir_ty/src/diagnostics/match_check.rs
+++ b/crates/hir_ty/src/diagnostics/match_check.rs
@@ -1335,6 +1335,23 @@ fn panic(a: Category, b: Category) {
         );
     }
 
+    #[test]
+    fn unknown_type() {
+        check_diagnostics(
+            r#"
+enum Option<T> { Some(T), None }
+
+fn main() {
+    // `Never` is deliberately not defined so that it's an uninferred type.
+    match Option::<Never>::None {
+        None => (),
+        Some(never) => match never {},
+    }
+}
+"#,
+        );
+    }
+
     mod false_negatives {
         //! The implementation of match checking here is a work in progress. As we roll this out, we
         //! prefer false negatives to false positives (ideally there would be no false positives). This
diff --git a/crates/hir_ty/src/traits.rs b/crates/hir_ty/src/traits.rs
index 255323717..14cd3a2b4 100644
--- a/crates/hir_ty/src/traits.rs
+++ b/crates/hir_ty/src/traits.rs
@@ -3,7 +3,7 @@ use std::sync::Arc;
 
 use base_db::CrateId;
 use chalk_ir::cast::Cast;
-use chalk_solve::Solver;
+use chalk_solve::{logging_db::LoggingRustIrDatabase, Solver};
 use hir_def::{lang_item::LangItemTarget, TraitId};
 
 use crate::{db::HirDatabase, DebruijnIndex, Substs};
@@ -166,16 +166,25 @@ fn solve(
         }
         remaining > 0
     };
+
     let mut solve = || {
-        let solution = solver.solve_limited(&context, goal, should_continue);
-        log::debug!("solve({:?}) => {:?}", goal, solution);
-        solution
+        if is_chalk_print() {
+            let logging_db = LoggingRustIrDatabase::new(context);
+            let solution = solver.solve_limited(&logging_db, goal, &should_continue);
+            log::debug!("chalk program:\n{}", logging_db);
+            solution
+        } else {
+            solver.solve_limited(&context, goal, &should_continue)
+        }
     };
+
     // don't set the TLS for Chalk unless Chalk debugging is active, to make
     // extra sure we only use it for debugging
     let solution =
         if is_chalk_debug() { chalk::tls::set_current_program(db, solve) } else { solve() };
 
+    log::debug!("solve({:?}) => {:?}", goal, solution);
+
     solution
 }
 
@@ -183,6 +192,10 @@ fn is_chalk_debug() -> bool {
     std::env::var("CHALK_DEBUG").is_ok()
 }
 
+fn is_chalk_print() -> bool {
+    std::env::var("CHALK_PRINT").is_ok()
+}
+
 fn solution_from_chalk(
     db: &dyn HirDatabase,
     solution: chalk_solve::Solution<Interner>,
diff --git a/crates/hir_ty/src/traits/chalk.rs b/crates/hir_ty/src/traits/chalk.rs
index b33653417..17c83b6a4 100644
--- a/crates/hir_ty/src/traits/chalk.rs
+++ b/crates/hir_ty/src/traits/chalk.rs
@@ -240,20 +240,23 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
         Substs::empty().to_chalk(self.db)
     }
 
-    fn trait_name(&self, _trait_id: chalk_ir::TraitId<Interner>) -> String {
-        unimplemented!()
+    fn trait_name(&self, trait_id: chalk_ir::TraitId<Interner>) -> String {
+        let id = from_chalk(self.db, trait_id);
+        self.db.trait_data(id).name.to_string()
     }
-    fn adt_name(&self, _struct_id: chalk_ir::AdtId<Interner>) -> String {
-        unimplemented!()
+    // FIXME: lookup names
+    fn adt_name(&self, struct_id: chalk_ir::AdtId<Interner>) -> String {
+        let datum = self.db.struct_datum(self.krate, struct_id);
+        format!("{:?}", datum.name(&Interner))
     }
-    fn assoc_type_name(&self, _assoc_ty_id: chalk_ir::AssocTypeId<Interner>) -> String {
-        unimplemented!()
+    fn assoc_type_name(&self, assoc_ty_id: chalk_ir::AssocTypeId<Interner>) -> String {
+        format!("Assoc_{}", assoc_ty_id.0)
     }
-    fn opaque_type_name(&self, _opaque_ty_id: chalk_ir::OpaqueTyId<Interner>) -> String {
-        unimplemented!()
+    fn opaque_type_name(&self, opaque_ty_id: chalk_ir::OpaqueTyId<Interner>) -> String {
+        format!("Opaque_{}", opaque_ty_id.0)
     }
-    fn fn_def_name(&self, _fn_def_id: chalk_ir::FnDefId<Interner>) -> String {
-        unimplemented!()
+    fn fn_def_name(&self, fn_def_id: chalk_ir::FnDefId<Interner>) -> String {
+        format!("fn_{}", fn_def_id.0)
     }
 }
 
diff --git a/crates/ide/src/completion/completion_context.rs b/crates/ide/src/completion/completion_context.rs
index 3857dce67..85456a66f 100644
--- a/crates/ide/src/completion/completion_context.rs
+++ b/crates/ide/src/completion/completion_context.rs
@@ -185,7 +185,7 @@ impl<'a> CompletionContext<'a> {
             };
             if let (Some(actual_expansion), Some(hypothetical_expansion)) = (
                 ctx.sema.expand(&actual_macro_call),
-                ctx.sema.expand_hypothetical(
+                ctx.sema.speculative_expand(
                     &actual_macro_call,
                     &hypothetical_args,
                     fake_ident_token,
diff --git a/crates/ide/src/inlay_hints.rs b/crates/ide/src/inlay_hints.rs
index 002adf915..596bc872d 100644
--- a/crates/ide/src/inlay_hints.rs
+++ b/crates/ide/src/inlay_hints.rs
@@ -43,7 +43,7 @@ pub struct InlayHint {
 // rust-analyzer shows additional information inline with the source code.
 // Editors usually render this using read-only virtual text snippets interspersed with code.
 //
-// rust-analyzer shows hits for
+// rust-analyzer shows hints for
 //
 // * types of local variables
 // * names of function arguments
diff --git a/crates/proc_macro_api/src/lib.rs b/crates/proc_macro_api/src/lib.rs
index 15db57eb2..d5e87cf7d 100644
--- a/crates/proc_macro_api/src/lib.rs
+++ b/crates/proc_macro_api/src/lib.rs
@@ -89,9 +89,8 @@ impl ProcMacroClient {
                 macros
                     .into_iter()
                     .filter_map(|(name, kind)| {
-                        // FIXME: Support custom derive only for now.
                         match kind {
-                            ProcMacroKind::CustomDerive => {
+                            ProcMacroKind::CustomDerive | ProcMacroKind::FuncLike => {
                                 let name = SmolStr::new(&name);
                                 let expander: Arc<dyn tt::TokenExpander> =
                                     Arc::new(ProcMacroProcessExpander {
@@ -101,7 +100,8 @@ impl ProcMacroClient {
                                     });
                                 Some((name, expander))
                             }
-                            _ => None,
+                            // FIXME: Attribute macro are currently unsupported.
+                            ProcMacroKind::Attr => None,
                         }
                     })
                     .collect()
diff --git a/crates/proc_macro_srv/Cargo.toml b/crates/proc_macro_srv/Cargo.toml
index 7171f0808..a468b5560 100644
--- a/crates/proc_macro_srv/Cargo.toml
+++ b/crates/proc_macro_srv/Cargo.toml
@@ -21,7 +21,9 @@ test_utils = { path = "../test_utils" }
 [dev-dependencies]
 cargo_metadata = "0.11.1"
 difference = "2.0.0"
-# used as proc macro test target
+
+# used as proc macro test targets
 serde_derive = "1.0.106"
+proc_macro_test = { path = "../proc_macro_test" }
 
 toolchain = { path = "../toolchain" }
diff --git a/crates/proc_macro_srv/src/tests/mod.rs b/crates/proc_macro_srv/src/tests/mod.rs
index 8e6f28abd..1a827cbd7 100644
--- a/crates/proc_macro_srv/src/tests/mod.rs
+++ b/crates/proc_macro_srv/src/tests/mod.rs
@@ -35,7 +35,7 @@ SUBTREE $
 
 #[test]
 fn test_derive_proc_macro_list() {
-    let res = list("serde_derive", "1.0").join("\n");
+    let res = list("serde_derive", "1").join("\n");
 
     assert_eq_text!(
         &res,
@@ -43,3 +43,16 @@ fn test_derive_proc_macro_list() {
 Deserialize [CustomDerive]"#
     );
 }
+
+/// Tests that we find and classify non-derive macros correctly.
+#[test]
+fn list_test_macros() {
+    let res = list("proc_macro_test", "0.0.0").join("\n");
+
+    assert_eq_text!(
+        &res,
+        r#"function_like_macro [FuncLike]
+attribute_macro [Attr]
+DummyTrait [CustomDerive]"#
+    );
+}
diff --git a/crates/proc_macro_srv/src/tests/utils.rs b/crates/proc_macro_srv/src/tests/utils.rs
index 5828512d6..36942147d 100644
--- a/crates/proc_macro_srv/src/tests/utils.rs
+++ b/crates/proc_macro_srv/src/tests/utils.rs
@@ -13,7 +13,7 @@ mod fixtures {
     // Use current project metadata to get the proc-macro dylib path
     pub fn dylib_path(crate_name: &str, version: &str) -> std::path::PathBuf {
         let command = Command::new(toolchain::cargo())
-            .args(&["check", "--message-format", "json"])
+            .args(&["check", "--tests", "--message-format", "json"])
             .output()
             .unwrap()
             .stdout;
diff --git a/crates/proc_macro_test/Cargo.toml b/crates/proc_macro_test/Cargo.toml
new file mode 100644
index 000000000..7b0f64f31
--- /dev/null
+++ b/crates/proc_macro_test/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "proc_macro_test"
+version = "0.0.0"
+license = "MIT OR Apache-2.0"
+authors = ["rust-analyzer developers"]
+edition = "2018"
+
+[lib]
+doctest = false
+proc-macro = true
diff --git a/crates/proc_macro_test/src/lib.rs b/crates/proc_macro_test/src/lib.rs
new file mode 100644
index 000000000..ec2a114a3
--- /dev/null
+++ b/crates/proc_macro_test/src/lib.rs
@@ -0,0 +1,18 @@
+//! Exports a few trivial procedural macros for testing.
+
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn function_like_macro(args: TokenStream) -> TokenStream {
+    args
+}
+
+#[proc_macro_attribute]
+pub fn attribute_macro(_args: TokenStream, item: TokenStream) -> TokenStream {
+    item
+}
+
+#[proc_macro_derive(DummyTrait)]
+pub fn derive_macro(_item: TokenStream) -> TokenStream {
+    TokenStream::new()
+}
diff --git a/crates/rust-analyzer/src/handlers.rs b/crates/rust-analyzer/src/handlers.rs
index 067f5ff66..4f77b1b4d 100644
--- a/crates/rust-analyzer/src/handlers.rs
+++ b/crates/rust-analyzer/src/handlers.rs
@@ -272,19 +272,24 @@ pub(crate) fn handle_document_symbol(
         parents.push((doc_symbol, symbol.parent));
     }
     let mut document_symbols = Vec::new();
+    // Constructs `document_symbols` from `parents`, in order from the end.
     while let Some((node, parent)) = parents.pop() {
         match parent {
             None => document_symbols.push(node),
             Some(i) => {
-                let children = &mut parents[i].0.children;
-                if children.is_none() {
-                    *children = Some(Vec::new());
-                }
-                children.as_mut().unwrap().push(node);
+                parents[i].0.children.get_or_insert_with(Vec::new).push(node);
             }
         }
     }
 
+    fn reverse(symbols: &mut Vec<DocumentSymbol>) {
+        for sym in symbols.iter_mut() {
+            sym.children.as_mut().map(|c| reverse(c));
+        }
+        symbols.reverse();
+    }
+    reverse(&mut document_symbols);
+
     let res = if snap.config.client_caps.hierarchical_symbols {
         document_symbols.into()
     } else {
@@ -863,10 +868,10 @@ pub(crate) fn handle_resolve_code_action(
         .map(|it| it.into_iter().filter_map(from_proto::assist_kind).collect());
 
     let assists = snap.analysis.resolved_assists(&snap.config.assist, frange)?;
-    let (id_string, index) = split_once(&params.id, ':').unwrap();
+    let (id, index) = split_once(&params.id, ':').unwrap();
     let index = index.parse::<usize>().unwrap();
     let assist = &assists[index];
-    assert!(assist.assist.id().0 == id_string);
+    assert!(assist.assist.id.0 == id);
     Ok(to_proto::resolved_code_action(&snap, assist.clone())?.edit)
 }
 
diff --git a/crates/rust-analyzer/src/lsp_ext.rs b/crates/rust-analyzer/src/lsp_ext.rs
index 3976b6529..e1a28b1b4 100644
--- a/crates/rust-analyzer/src/lsp_ext.rs
+++ b/crates/rust-analyzer/src/lsp_ext.rs
@@ -237,8 +237,13 @@ pub enum Status {
     Invalid,
 }
 
+#[derive(Deserialize, Serialize)]
+pub struct StatusParams {
+    pub status: Status,
+}
+
 impl Notification for StatusNotification {
-    type Params = Status;
+    type Params = StatusParams;
     const METHOD: &'static str = "rust-analyzer/status";
 }
 
diff --git a/crates/rust-analyzer/src/reload.rs b/crates/rust-analyzer/src/reload.rs
index a2cfb4e0d..505505a77 100644
--- a/crates/rust-analyzer/src/reload.rs
+++ b/crates/rust-analyzer/src/reload.rs
@@ -13,6 +13,7 @@ use crate::{
     lsp_ext,
     main_loop::Task,
 };
+use lsp_ext::StatusParams;
 
 impl GlobalState {
     pub(crate) fn update_configuration(&mut self, config: Config) {
@@ -85,7 +86,9 @@ impl GlobalState {
                 Status::Invalid => lsp_ext::Status::Invalid,
                 Status::NeedsReload => lsp_ext::Status::NeedsReload,
             };
-            self.send_notification::<lsp_ext::StatusNotification>(lsp_status);
+            self.send_notification::<lsp_ext::StatusNotification>(StatusParams {
+                status: lsp_status,
+            });
         }
     }
     pub(crate) fn fetch_workspaces(&mut self) {
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index 8a2cfa2ae..535de2f71 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -704,10 +704,10 @@ pub(crate) fn unresolved_code_action(
     index: usize,
 ) -> Result<lsp_ext::CodeAction> {
     let res = lsp_ext::CodeAction {
-        title: assist.label(),
-        id: Some(format!("{}:{}", assist.id().0.to_owned(), index.to_string())),
-        group: assist.group().filter(|_| snap.config.client_caps.code_action_group).map(|gr| gr.0),
-        kind: Some(code_action_kind(assist.id().1)),
+        title: assist.label().to_string(),
+        id: Some(format!("{}:{}", assist.id.0, index.to_string())),
+        group: assist.group.filter(|_| snap.config.client_caps.code_action_group).map(|gr| gr.0),
+        kind: Some(code_action_kind(assist.id.1)),
         edit: None,
         is_preferred: None,
     };
diff --git a/crates/rust-analyzer/tests/heavy_tests/main.rs b/crates/rust-analyzer/tests/rust-analyzer/main.rs
index 7370505f8..fa315ff8e 100644
--- a/crates/rust-analyzer/tests/heavy_tests/main.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/main.rs
@@ -1,3 +1,13 @@
+//! The most high-level integrated tests for rust-analyzer.
+//!
+//! This tests run a full LSP event loop, spawn cargo and process stdlib from
+//! sysroot. For this reason, the tests here are very slow, and should be
+//! avoided unless absolutely necessary.
+//!
+//! In particular, it's fine *not* to test that client & server agree on
+//! specific JSON shapes here -- there's little value in such tests, as we can't
+//! be sure without a real client anyway.
+
 mod testdir;
 mod support;
 
diff --git a/crates/rust-analyzer/tests/heavy_tests/support.rs b/crates/rust-analyzer/tests/rust-analyzer/support.rs
index 5bafeba79..5bafeba79 100644
--- a/crates/rust-analyzer/tests/heavy_tests/support.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/support.rs
diff --git a/crates/rust-analyzer/tests/heavy_tests/testdir.rs b/crates/rust-analyzer/tests/rust-analyzer/testdir.rs
index 7487e7429..7487e7429 100644
--- a/crates/rust-analyzer/tests/heavy_tests/testdir.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/testdir.rs
diff --git a/crates/ssr/Cargo.toml b/crates/ssr/Cargo.toml
index 56c1f7761..7c2090de3 100644
--- a/crates/ssr/Cargo.toml
+++ b/crates/ssr/Cargo.toml
@@ -12,6 +12,7 @@ doctest = false
 
 [dependencies]
 rustc-hash = "1.1.0"
+itertools = "0.9.0"
 
 text_edit = { path = "../text_edit" }
 syntax = { path = "../syntax" }
diff --git a/crates/ssr/src/lib.rs b/crates/ssr/src/lib.rs
index 292bd5b9a..ba669fd56 100644
--- a/crates/ssr/src/lib.rs
+++ b/crates/ssr/src/lib.rs
@@ -21,7 +21,10 @@
 // code in the `foo` module, we'll insert just `Bar`.
 //
 // Inherent method calls should generally be written in UFCS form. e.g. `foo::Bar::baz($s, $a)` will
-// match `$s.baz($a)`, provided the method call `baz` resolves to the method `foo::Bar::baz`.
+// match `$s.baz($a)`, provided the method call `baz` resolves to the method `foo::Bar::baz`. When a
+// placeholder is the receiver of a method call in the search pattern (e.g. `$s.foo()`), but not in
+// the replacement template (e.g. `bar($s)`), then *, & and &mut will be added as needed to mirror
+// whatever autoderef and autoref was happening implicitly in the matched code.
 //
 // The scope of the search / replace will be restricted to the current selection if any, otherwise
 // it will apply to the whole workspace.
diff --git a/crates/ssr/src/matching.rs b/crates/ssr/src/matching.rs
index ffc7202ae..8bb5ced90 100644
--- a/crates/ssr/src/matching.rs
+++ b/crates/ssr/src/matching.rs
@@ -2,7 +2,7 @@
 //! process of matching, placeholder values are recorded.
 
 use crate::{
-    parsing::{Constraint, NodeKind, Placeholder},
+    parsing::{Constraint, NodeKind, Placeholder, Var},
     resolving::{ResolvedPattern, ResolvedRule, UfcsCallInfo},
     SsrMatches,
 };
@@ -56,10 +56,6 @@ pub struct Match {
     pub(crate) rendered_template_paths: FxHashMap<SyntaxNode, hir::ModPath>,
 }
 
-/// Represents a `$var` in an SSR query.
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub(crate) struct Var(pub String);
-
 /// Information about a placeholder bound in a match.
 #[derive(Debug)]
 pub(crate) struct PlaceholderMatch {
@@ -69,6 +65,10 @@ pub(crate) struct PlaceholderMatch {
     pub(crate) range: FileRange,
     /// More matches, found within `node`.
     pub(crate) inner_matches: SsrMatches,
+    /// How many times the code that the placeholder matched needed to be dereferenced. Will only be
+    /// non-zero if the placeholder matched to the receiver of a method call.
+    pub(crate) autoderef_count: usize,
+    pub(crate) autoref_kind: ast::SelfParamKind,
 }
 
 #[derive(Debug)]
@@ -173,7 +173,7 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
         code: &SyntaxNode,
     ) -> Result<(), MatchFailed> {
         // Handle placeholders.
-        if let Some(placeholder) = self.get_placeholder(&SyntaxElement::Node(pattern.clone())) {
+        if let Some(placeholder) = self.get_placeholder_for_node(pattern) {
             for constraint in &placeholder.constraints {
                 self.check_constraint(constraint, code)?;
             }
@@ -183,8 +183,8 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
                 // probably can't fail range validation, but just to be safe...
                 self.validate_range(&original_range)?;
                 matches_out.placeholder_values.insert(
-                    Var(placeholder.ident.to_string()),
-                    PlaceholderMatch::new(code, original_range),
+                    placeholder.ident.clone(),
+                    PlaceholderMatch::new(Some(code), original_range),
                 );
             }
             return Ok(());
@@ -487,7 +487,7 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
                 }
                 if let Phase::Second(match_out) = phase {
                     match_out.placeholder_values.insert(
-                        Var(placeholder.ident.to_string()),
+                        placeholder.ident.clone(),
                         PlaceholderMatch::from_range(FileRange {
                             file_id: self.sema.original_range(code).file_id,
                             range: first_matched_token
@@ -536,18 +536,40 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
         if pattern_ufcs.function != code_resolved_function {
             fail_match!("Method call resolved to a different function");
         }
-        if code_resolved_function.has_self_param(self.sema.db) {
-            if let (Some(pattern_type), Some(expr)) = (&pattern_ufcs.qualifier_type, &code.expr()) {
-                self.check_expr_type(pattern_type, expr)?;
-            }
-        }
         // Check arguments.
         let mut pattern_args = pattern_ufcs
             .call_expr
             .arg_list()
             .ok_or_else(|| match_error!("Pattern function call has no args"))?
             .args();
-        self.attempt_match_opt(phase, pattern_args.next(), code.expr())?;
+        // If the function we're calling takes a self parameter, then we store additional
+        // information on the placeholder match about autoderef and autoref. This allows us to use
+        // the placeholder in a context where autoderef and autoref don't apply.
+        if code_resolved_function.has_self_param(self.sema.db) {
+            if let (Some(pattern_type), Some(expr)) = (&pattern_ufcs.qualifier_type, &code.expr()) {
+                let deref_count = self.check_expr_type(pattern_type, expr)?;
+                let pattern_receiver = pattern_args.next();
+                self.attempt_match_opt(phase, pattern_receiver.clone(), code.expr())?;
+                if let Phase::Second(match_out) = phase {
+                    if let Some(placeholder_value) = pattern_receiver
+                        .and_then(|n| self.get_placeholder_for_node(n.syntax()))
+                        .and_then(|placeholder| {
+                            match_out.placeholder_values.get_mut(&placeholder.ident)
+                        })
+                    {
+                        placeholder_value.autoderef_count = deref_count;
+                        placeholder_value.autoref_kind = self
+                            .sema
+                            .resolve_method_call_as_callable(code)
+                            .and_then(|callable| callable.receiver_param(self.sema.db))
+                            .map(|self_param| self_param.kind())
+                            .unwrap_or(ast::SelfParamKind::Owned);
+                    }
+                }
+            }
+        } else {
+            self.attempt_match_opt(phase, pattern_args.next(), code.expr())?;
+        }
         let mut code_args =
             code.arg_list().ok_or_else(|| match_error!("Code method call has no args"))?.args();
         loop {
@@ -575,26 +597,35 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
         self.attempt_match_node_children(phase, pattern_ufcs.call_expr.syntax(), code.syntax())
     }
 
+    /// Verifies that `expr` matches `pattern_type`, possibly after dereferencing some number of
+    /// times. Returns the number of times it needed to be dereferenced.
     fn check_expr_type(
         &self,
         pattern_type: &hir::Type,
         expr: &ast::Expr,
-    ) -> Result<(), MatchFailed> {
+    ) -> Result<usize, MatchFailed> {
         use hir::HirDisplay;
         let code_type = self.sema.type_of_expr(&expr).ok_or_else(|| {
             match_error!("Failed to get receiver type for `{}`", expr.syntax().text())
         })?;
-        if !code_type
+        // Temporary needed to make the borrow checker happy.
+        let res = code_type
             .autoderef(self.sema.db)
-            .any(|deref_code_type| *pattern_type == deref_code_type)
-        {
-            fail_match!(
-                "Pattern type `{}` didn't match code type `{}`",
-                pattern_type.display(self.sema.db),
-                code_type.display(self.sema.db)
-            );
-        }
-        Ok(())
+            .enumerate()
+            .find(|(_, deref_code_type)| pattern_type == deref_code_type)
+            .map(|(count, _)| count)
+            .ok_or_else(|| {
+                match_error!(
+                    "Pattern type `{}` didn't match code type `{}`",
+                    pattern_type.display(self.sema.db),
+                    code_type.display(self.sema.db)
+                )
+            });
+        res
+    }
+
+    fn get_placeholder_for_node(&self, node: &SyntaxNode) -> Option<&Placeholder> {
+        self.get_placeholder(&SyntaxElement::Node(node.clone()))
     }
 
     fn get_placeholder(&self, element: &SyntaxElement) -> Option<&Placeholder> {
@@ -676,12 +707,18 @@ fn recording_match_fail_reasons() -> bool {
 }
 
 impl PlaceholderMatch {
-    fn new(node: &SyntaxNode, range: FileRange) -> Self {
-        Self { node: Some(node.clone()), range, inner_matches: SsrMatches::default() }
+    fn new(node: Option<&SyntaxNode>, range: FileRange) -> Self {
+        Self {
+            node: node.cloned(),
+            range,
+            inner_matches: SsrMatches::default(),
+            autoderef_count: 0,
+            autoref_kind: ast::SelfParamKind::Owned,
+        }
     }
 
     fn from_range(range: FileRange) -> Self {
-        Self { node: None, range, inner_matches: SsrMatches::default() }
+        Self::new(None, range)
     }
 }
 
diff --git a/crates/ssr/src/parsing.rs b/crates/ssr/src/parsing.rs
index 9570e96e3..05b66dcd7 100644
--- a/crates/ssr/src/parsing.rs
+++ b/crates/ssr/src/parsing.rs
@@ -8,7 +8,7 @@
 use crate::errors::bail;
 use crate::{SsrError, SsrPattern, SsrRule};
 use rustc_hash::{FxHashMap, FxHashSet};
-use std::str::FromStr;
+use std::{fmt::Display, str::FromStr};
 use syntax::{ast, AstNode, SmolStr, SyntaxKind, SyntaxNode, T};
 use test_utils::mark;
 
@@ -34,12 +34,16 @@ pub(crate) enum PatternElement {
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub(crate) struct Placeholder {
     /// The name of this placeholder. e.g. for "$a", this would be "a"
-    pub(crate) ident: SmolStr,
+    pub(crate) ident: Var,
     /// A unique name used in place of this placeholder when we parse the pattern as Rust code.
     stand_in_name: String,
     pub(crate) constraints: Vec<Constraint>,
 }
 
+/// Represents a `$var` in an SSR query.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub(crate) struct Var(pub String);
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub(crate) enum Constraint {
     Kind(NodeKind),
@@ -205,7 +209,7 @@ fn parse_pattern(pattern_str: &str) -> Result<Vec<PatternElement>, SsrError> {
         if token.kind == T![$] {
             let placeholder = parse_placeholder(&mut tokens)?;
             if !placeholder_names.insert(placeholder.ident.clone()) {
-                bail!("Name `{}` repeats more than once", placeholder.ident);
+                bail!("Placeholder `{}` repeats more than once", placeholder.ident);
             }
             res.push(PatternElement::Placeholder(placeholder));
         } else {
@@ -228,7 +232,7 @@ fn validate_rule(rule: &SsrRule) -> Result<(), SsrError> {
     for p in &rule.template.tokens {
         if let PatternElement::Placeholder(placeholder) = p {
             if !defined_placeholders.contains(&placeholder.ident) {
-                undefined.push(format!("${}", placeholder.ident));
+                undefined.push(placeholder.ident.to_string());
             }
             if !placeholder.constraints.is_empty() {
                 bail!("Replacement placeholders cannot have constraints");
@@ -344,7 +348,17 @@ impl NodeKind {
 
 impl Placeholder {
     fn new(name: SmolStr, constraints: Vec<Constraint>) -> Self {
-        Self { stand_in_name: format!("__placeholder_{}", name), constraints, ident: name }
+        Self {
+            stand_in_name: format!("__placeholder_{}", name),
+            constraints,
+            ident: Var(name.to_string()),
+        }
+    }
+}
+
+impl Display for Var {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "${}", self.0)
     }
 }
 
diff --git a/crates/ssr/src/replacing.rs b/crates/ssr/src/replacing.rs
index 8f8fe6149..29284e3f1 100644
--- a/crates/ssr/src/replacing.rs
+++ b/crates/ssr/src/replacing.rs
@@ -1,10 +1,11 @@
 //! Code for applying replacement templates for matches that have previously been found.
 
-use crate::matching::Var;
 use crate::{resolving::ResolvedRule, Match, SsrMatches};
+use itertools::Itertools;
 use rustc_hash::{FxHashMap, FxHashSet};
 use syntax::ast::{self, AstToken};
 use syntax::{SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken, TextRange, TextSize};
+use test_utils::mark;
 use text_edit::TextEdit;
 
 /// Returns a text edit that will replace each match in `matches` with its corresponding replacement
@@ -114,11 +115,33 @@ impl ReplacementRenderer<'_> {
     fn render_token(&mut self, token: &SyntaxToken) {
         if let Some(placeholder) = self.rule.get_placeholder(&token) {
             if let Some(placeholder_value) =
-                self.match_info.placeholder_values.get(&Var(placeholder.ident.to_string()))
+                self.match_info.placeholder_values.get(&placeholder.ident)
             {
                 let range = &placeholder_value.range.range;
                 let mut matched_text =
                     self.file_src[usize::from(range.start())..usize::from(range.end())].to_owned();
+                // If a method call is performed directly on the placeholder, then autoderef and
+                // autoref will apply, so we can just substitute whatever the placeholder matched to
+                // directly. If we're not applying a method call, then we need to add explicitly
+                // deref and ref in order to match whatever was being done implicitly at the match
+                // site.
+                if !token_is_method_call_receiver(token)
+                    && (placeholder_value.autoderef_count > 0
+                        || placeholder_value.autoref_kind != ast::SelfParamKind::Owned)
+                {
+                    mark::hit!(replace_autoref_autoderef_capture);
+                    let ref_kind = match placeholder_value.autoref_kind {
+                        ast::SelfParamKind::Owned => "",
+                        ast::SelfParamKind::Ref => "&",
+                        ast::SelfParamKind::MutRef => "&mut ",
+                    };
+                    matched_text = format!(
+                        "{}{}{}",
+                        ref_kind,
+                        "*".repeat(placeholder_value.autoderef_count),
+                        matched_text
+                    );
+                }
                 let edit = matches_to_edit_at_offset(
                     &placeholder_value.inner_matches,
                     self.file_src,
@@ -179,6 +202,29 @@ impl ReplacementRenderer<'_> {
     }
 }
 
+/// Returns whether token is the receiver of a method call. Note, being within the receiver of a
+/// method call doesn't count. e.g. if the token is `$a`, then `$a.foo()` will return true, while
+/// `($a + $b).foo()` or `x.foo($a)` will return false.
+fn token_is_method_call_receiver(token: &SyntaxToken) -> bool {
+    use syntax::ast::AstNode;
+    // Find the first method call among the ancestors of `token`, then check if the only token
+    // within the receiver is `token`.
+    if let Some(receiver) =
+        token.ancestors().find_map(ast::MethodCallExpr::cast).and_then(|call| call.expr())
+    {
+        let tokens = receiver.syntax().descendants_with_tokens().filter_map(|node_or_token| {
+            match node_or_token {
+                SyntaxElement::Token(t) => Some(t),
+                _ => None,
+            }
+        });
+        if let Some((only_token,)) = tokens.collect_tuple() {
+            return only_token == *token;
+        }
+    }
+    false
+}
+
 fn parse_as_kind(code: &str, kind: SyntaxKind) -> Option<SyntaxNode> {
     use syntax::ast::AstNode;
     if ast::Expr::can_cast(kind) {
diff --git a/crates/ssr/src/resolving.rs b/crates/ssr/src/resolving.rs
index 4441fb426..b932132d5 100644
--- a/crates/ssr/src/resolving.rs
+++ b/crates/ssr/src/resolving.rs
@@ -212,13 +212,13 @@ impl<'db> ResolutionScope<'db> {
         // First try resolving the whole path. This will work for things like
         // `std::collections::HashMap`, but will fail for things like
         // `std::collections::HashMap::new`.
-        if let Some(resolution) = self.scope.resolve_hypothetical(&path) {
+        if let Some(resolution) = self.scope.speculative_resolve(&path) {
             return Some(resolution);
         }
         // Resolution failed, try resolving the qualifier (e.g. `std::collections::HashMap` and if
         // that succeeds, then iterate through the candidates on the resolved type with the provided
         // name.
-        let resolved_qualifier = self.scope.resolve_hypothetical(&path.qualifier()?)?;
+        let resolved_qualifier = self.scope.speculative_resolve(&path.qualifier()?)?;
         if let hir::PathResolution::Def(hir::ModuleDef::Adt(adt)) = resolved_qualifier {
             let name = path.segment()?.name_ref()?;
             adt.ty(self.scope.db).iterate_path_candidates(
diff --git a/crates/ssr/src/tests.rs b/crates/ssr/src/tests.rs
index 0d0a00090..e45c88864 100644
--- a/crates/ssr/src/tests.rs
+++ b/crates/ssr/src/tests.rs
@@ -31,7 +31,7 @@ fn parser_two_delimiters() {
 fn parser_repeated_name() {
     assert_eq!(
         parse_error_text("foo($a, $a) ==>>"),
-        "Parse error: Name `a` repeats more than once"
+        "Parse error: Placeholder `$a` repeats more than once"
     );
 }
 
@@ -1172,3 +1172,110 @@ fn match_trait_method_call() {
     assert_matches("Bar::foo($a, $b)", code, &["v1.foo(1)", "Bar::foo(&v1, 3)", "v1_ref.foo(5)"]);
     assert_matches("Bar2::foo($a, $b)", code, &["v2.foo(2)", "Bar2::foo(&v2, 4)", "v2_ref.foo(6)"]);
 }
+
+#[test]
+fn replace_autoref_autoderef_capture() {
+    // Here we have several calls to `$a.foo()`. In the first case autoref is applied, in the
+    // second, we already have a reference, so it isn't. When $a is used in a context where autoref
+    // doesn't apply, we need to prefix it with `&`. Finally, we have some cases where autoderef
+    // needs to be applied.
+    mark::check!(replace_autoref_autoderef_capture);
+    let code = r#"
+        struct Foo {}
+        impl Foo {
+            fn foo(&self) {}
+            fn foo2(&self) {}
+        }
+        fn bar(_: &Foo) {}
+        fn main() {
+            let f = Foo {};
+            let fr = &f;
+            let fr2 = &fr;
+            let fr3 = &fr2;
+            f.foo();
+            fr.foo();
+            fr2.foo();
+            fr3.foo();
+        }
+        "#;
+    assert_ssr_transform(
+        "Foo::foo($a) ==>> bar($a)",
+        code,
+        expect![[r#"
+            struct Foo {}
+            impl Foo {
+                fn foo(&self) {}
+                fn foo2(&self) {}
+            }
+            fn bar(_: &Foo) {}
+            fn main() {
+                let f = Foo {};
+                let fr = &f;
+                let fr2 = &fr;
+                let fr3 = &fr2;
+                bar(&f);
+                bar(&*fr);
+                bar(&**fr2);
+                bar(&***fr3);
+            }
+        "#]],
+    );
+    // If the placeholder is used as the receiver of another method call, then we don't need to
+    // explicitly autoderef or autoref.
+    assert_ssr_transform(
+        "Foo::foo($a) ==>> $a.foo2()",
+        code,
+        expect![[r#"
+            struct Foo {}
+            impl Foo {
+                fn foo(&self) {}
+                fn foo2(&self) {}
+            }
+            fn bar(_: &Foo) {}
+            fn main() {
+                let f = Foo {};
+                let fr = &f;
+                let fr2 = &fr;
+                let fr3 = &fr2;
+                f.foo2();
+                fr.foo2();
+                fr2.foo2();
+                fr3.foo2();
+            }
+        "#]],
+    );
+}
+
+#[test]
+fn replace_autoref_mut() {
+    let code = r#"
+        struct Foo {}
+        impl Foo {
+            fn foo(&mut self) {}
+        }
+        fn bar(_: &mut Foo) {}
+        fn main() {
+            let mut f = Foo {};
+            f.foo();
+            let fr = &mut f;
+            fr.foo();
+        }
+        "#;
+    assert_ssr_transform(
+        "Foo::foo($a) ==>> bar($a)",
+        code,
+        expect![[r#"
+            struct Foo {}
+            impl Foo {
+                fn foo(&mut self) {}
+            }
+            fn bar(_: &mut Foo) {}
+            fn main() {
+                let mut f = Foo {};
+                bar(&mut f);
+                let fr = &mut f;
+                bar(&mut *fr);
+            }
+        "#]],
+    );
+}
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index 3c5027fe5..265d19288 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -17,7 +17,7 @@ pub fn timeit(label: &'static str) -> impl Drop {
 
     impl Drop for Guard {
         fn drop(&mut self) {
-            eprintln!("{}: {:?}", self.label, self.start.elapsed())
+            eprintln!("{}: {:.2?}", self.label, self.start.elapsed())
         }
     }
 
diff --git a/crates/syntax/Cargo.toml b/crates/syntax/Cargo.toml
index 47e351f9d..ec3132da8 100644
--- a/crates/syntax/Cargo.toml
+++ b/crates/syntax/Cargo.toml
@@ -13,7 +13,7 @@ doctest = false
 [dependencies]
 itertools = "0.9.0"
 rowan = "0.10.0"
-rustc_lexer = { version = "671.0.0", package = "rustc-ap-rustc_lexer" }
+rustc_lexer = { version = "673.0.0", package = "rustc-ap-rustc_lexer" }
 rustc-hash = "1.1.0"
 arrayvec = "0.5.1"
 once_cell = "1.3.1"
diff --git a/crates/syntax/src/ast/edit.rs b/crates/syntax/src/ast/edit.rs
index 190746e09..060b20966 100644
--- a/crates/syntax/src/ast/edit.rs
+++ b/crates/syntax/src/ast/edit.rs
@@ -91,29 +91,52 @@ impl ast::AssocItemList {
             res = make_multiline(res);
         }
         items.into_iter().for_each(|it| res = res.append_item(it));
-        res
+        res.fixup_trailing_whitespace().unwrap_or(res)
     }
 
     #[must_use]
     pub fn append_item(&self, item: ast::AssocItem) -> ast::AssocItemList {
-        let (indent, position) = match self.assoc_items().last() {
+        let (indent, position, whitespace) = match self.assoc_items().last() {
             Some(it) => (
                 leading_indent(it.syntax()).unwrap_or_default().to_string(),
                 InsertPosition::After(it.syntax().clone().into()),
+                "\n\n",
             ),
             None => match self.l_curly_token() {
                 Some(it) => (
                     "    ".to_string() + &leading_indent(self.syntax()).unwrap_or_default(),
                     InsertPosition::After(it.into()),
+                    "\n",
                 ),
                 None => return self.clone(),
             },
         };
-        let ws = tokens::WsBuilder::new(&format!("\n{}", indent));
+        let ws = tokens::WsBuilder::new(&format!("{}{}", whitespace, indent));
         let to_insert: ArrayVec<[SyntaxElement; 2]> =
             [ws.ws().into(), item.syntax().clone().into()].into();
         self.insert_children(position, to_insert)
     }
+
+    /// Remove extra whitespace between last item and closing curly brace.
+    fn fixup_trailing_whitespace(&self) -> Option<ast::AssocItemList> {
+        let first_token_after_items =
+            self.assoc_items().last()?.syntax().next_sibling_or_token()?;
+        let last_token_before_curly = self.r_curly_token()?.prev_sibling_or_token()?;
+        if last_token_before_curly != first_token_after_items {
+            // there is something more between last item and
+            // right curly than just whitespace - bail out
+            return None;
+        }
+        let whitespace =
+            last_token_before_curly.clone().into_token().and_then(ast::Whitespace::cast)?;
+        let text = whitespace.syntax().text();
+        let newline = text.rfind("\n")?;
+        let keep = tokens::WsBuilder::new(&text[newline..]);
+        Some(self.replace_children(
+            first_token_after_items..=last_token_before_curly,
+            std::iter::once(keep.ws().into()),
+        ))
+    }
 }
 
 impl ast::RecordExprFieldList {
diff --git a/crates/vfs/src/vfs_path.rs b/crates/vfs/src/vfs_path.rs
index 04a42264e..944a702df 100644
--- a/crates/vfs/src/vfs_path.rs
+++ b/crates/vfs/src/vfs_path.rs
@@ -57,23 +57,42 @@ impl VfsPath {
         };
         buf.push(tag);
         match &self.0 {
-            VfsPathRepr::PathBuf(it) => {
-                let path: &std::ffi::OsStr = it.as_os_str();
+            VfsPathRepr::PathBuf(path) => {
                 #[cfg(windows)]
                 {
-                    use std::os::windows::ffi::OsStrExt;
-                    for wchar in path.encode_wide() {
-                        buf.extend(wchar.to_le_bytes().iter().copied());
+                    use windows_paths::Encode;
+                    let components = path.components();
+                    let mut add_sep = false;
+                    for component in components {
+                        if add_sep {
+                            windows_paths::SEP.encode(buf);
+                        }
+                        let len_before = buf.len();
+                        match component {
+                            std::path::Component::Prefix(prefix) => {
+                                // kind() returns a normalized and comparable path prefix.
+                                prefix.kind().encode(buf);
+                            }
+                            std::path::Component::RootDir => {
+                                if !add_sep {
+                                    component.as_os_str().encode(buf);
+                                }
+                            }
+                            _ => component.as_os_str().encode(buf),
+                        }
+
+                        // some components may be encoded empty
+                        add_sep = len_before != buf.len();
                     }
                 }
                 #[cfg(unix)]
                 {
                     use std::os::unix::ffi::OsStrExt;
-                    buf.extend(path.as_bytes());
+                    buf.extend(path.as_os_str().as_bytes());
                 }
                 #[cfg(not(any(windows, unix)))]
                 {
-                    buf.extend(path.to_string_lossy().as_bytes());
+                    buf.extend(path.as_os_str().to_string_lossy().as_bytes());
                 }
             }
             VfsPathRepr::VirtualPath(VirtualPath(s)) => buf.extend(s.as_bytes()),
@@ -81,6 +100,112 @@ impl VfsPath {
     }
 }
 
+#[cfg(windows)]
+mod windows_paths {
+    pub trait Encode {
+        fn encode(&self, buf: &mut Vec<u8>);
+    }
+
+    impl Encode for std::ffi::OsStr {
+        fn encode(&self, buf: &mut Vec<u8>) {
+            use std::os::windows::ffi::OsStrExt;
+            for wchar in self.encode_wide() {
+                buf.extend(wchar.to_le_bytes().iter().copied());
+            }
+        }
+    }
+
+    impl Encode for u8 {
+        fn encode(&self, buf: &mut Vec<u8>) {
+            let wide = *self as u16;
+            buf.extend(wide.to_le_bytes().iter().copied())
+        }
+    }
+
+    impl Encode for &str {
+        fn encode(&self, buf: &mut Vec<u8>) {
+            debug_assert!(self.is_ascii());
+            for b in self.as_bytes() {
+                b.encode(buf)
+            }
+        }
+    }
+
+    pub const SEP: &str = "\\";
+    const VERBATIM: &str = "\\\\?\\";
+    const UNC: &str = "UNC";
+    const DEVICE: &str = "\\\\.\\";
+    const COLON: &str = ":";
+
+    impl Encode for std::path::Prefix<'_> {
+        fn encode(&self, buf: &mut Vec<u8>) {
+            match self {
+                std::path::Prefix::Verbatim(c) => {
+                    VERBATIM.encode(buf);
+                    c.encode(buf);
+                }
+                std::path::Prefix::VerbatimUNC(server, share) => {
+                    VERBATIM.encode(buf);
+                    UNC.encode(buf);
+                    SEP.encode(buf);
+                    server.encode(buf);
+                    SEP.encode(buf);
+                    share.encode(buf);
+                }
+                std::path::Prefix::VerbatimDisk(d) => {
+                    VERBATIM.encode(buf);
+                    d.encode(buf);
+                    COLON.encode(buf);
+                }
+                std::path::Prefix::DeviceNS(device) => {
+                    DEVICE.encode(buf);
+                    device.encode(buf);
+                }
+                std::path::Prefix::UNC(server, share) => {
+                    SEP.encode(buf);
+                    SEP.encode(buf);
+                    server.encode(buf);
+                    SEP.encode(buf);
+                    share.encode(buf);
+                }
+                std::path::Prefix::Disk(d) => {
+                    d.encode(buf);
+                    COLON.encode(buf);
+                }
+            }
+        }
+    }
+    #[test]
+    fn paths_encoding() {
+        // drive letter casing agnostic
+        test_eq("C:/x.rs", "c:/x.rs");
+        // separator agnostic
+        test_eq("C:/x/y.rs", "C:\\x\\y.rs");
+
+        fn test_eq(a: &str, b: &str) {
+            let mut b1 = Vec::new();
+            let mut b2 = Vec::new();
+            vfs(a).encode(&mut b1);
+            vfs(b).encode(&mut b2);
+            assert_eq!(b1, b2);
+        }
+    }
+
+    #[test]
+    fn test_sep_root_dir_encoding() {
+        let mut buf = Vec::new();
+        vfs("C:/x/y").encode(&mut buf);
+        assert_eq!(&buf, &[0, 67, 0, 58, 0, 92, 0, 120, 0, 92, 0, 121, 0])
+    }
+
+    #[cfg(test)]
+    fn vfs(str: &str) -> super::VfsPath {
+        use super::{AbsPathBuf, VfsPath};
+        use std::convert::TryFrom;
+        VfsPath::from(AbsPathBuf::try_from(str).unwrap())
+    }
+}
+
 #[derive(Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
 enum VfsPathRepr {
     PathBuf(AbsPathBuf),