38 files changed, 694 insertions, 114 deletions

diff --git a/crates/ra_assists/src/assist_ctx.rs b/crates/ra_assists/src/assist_ctx.rs
index 43f0d664b..2ab65ab99 100644
--- a/crates/ra_assists/src/assist_ctx.rs
+++ b/crates/ra_assists/src/assist_ctx.rs
@@ -101,7 +101,6 @@ impl<'a, DB: HirDatabase> AssistCtx<'a, DB> {
         Some(assist)
     }
 
-    #[allow(dead_code)] // will be used for auto import assist with multiple actions
     pub(crate) fn add_assist_group(
         self,
         id: AssistId,
@@ -168,7 +167,6 @@ pub(crate) struct ActionBuilder {
 }
 
 impl ActionBuilder {
-    #[allow(dead_code)]
     /// Adds a custom label to the action, if it needs to be different from the assist label
     pub(crate) fn label(&mut self, label: impl Into<String>) {
         self.label = Some(label.into())
diff --git a/crates/ra_assists/src/assists/add_explicit_type.rs b/crates/ra_assists/src/assists/add_explicit_type.rs
index f9f826b88..38a351a54 100644
--- a/crates/ra_assists/src/assists/add_explicit_type.rs
+++ b/crates/ra_assists/src/assists/add_explicit_type.rs
@@ -1,7 +1,7 @@
 use hir::{db::HirDatabase, HirDisplay};
 use ra_syntax::{
     ast::{self, AstNode, LetStmt, NameOwner},
-    T,
+    TextRange, T,
 };
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -34,6 +34,14 @@ pub(crate) fn add_explicit_type(ctx: AssistCtx<impl HirDatabase>) -> Option<Assi
     // The binding must have a name
     let name = pat.name()?;
     let name_range = name.syntax().text_range();
+    // Assist should only be applicable if cursor is between 'let' and '='
+    let stmt_range = stmt.syntax().text_range();
+    let eq_range = stmt.eq_token()?.text_range();
+    let let_range = TextRange::from_to(stmt_range.start(), eq_range.start());
+    let cursor_in_range = ctx.frange.range.is_subrange(&let_range);
+    if !cursor_in_range {
+        return None;
+    }
     // Assist not applicable if the type has already been specified
     if stmt.syntax().children_with_tokens().any(|child| child.kind() == T![:]) {
         return None;
@@ -109,4 +117,20 @@ mod tests {
     fn add_explicit_type_not_applicable_if_specified_ty_is_tuple() {
         check_assist_not_applicable(add_explicit_type, "fn f() { let a<|>: (i32, i32) = (3, 4); }");
     }
+
+    #[test]
+    fn add_explicit_type_not_applicable_if_cursor_after_equals() {
+        check_assist_not_applicable(
+            add_explicit_type,
+            "fn f() {let a =<|> match 1 {2 => 3, 3 => 5};}",
+        )
+    }
+
+    #[test]
+    fn add_explicit_type_not_applicable_if_cursor_before_let() {
+        check_assist_not_applicable(
+            add_explicit_type,
+            "fn f() <|>{let a = match 1 {2 => 3, 3 => 5};}",
+        )
+    }
 }
diff --git a/crates/ra_assists/src/assists/auto_import.rs b/crates/ra_assists/src/assists/auto_import.rs
new file mode 100644
index 000000000..9163cc662
--- /dev/null
+++ b/crates/ra_assists/src/assists/auto_import.rs
@@ -0,0 +1,222 @@
+use hir::db::HirDatabase;
+use ra_syntax::{
+    ast::{self, AstNode},
+    SmolStr, SyntaxElement,
+    SyntaxKind::{NAME_REF, USE_ITEM},
+    SyntaxNode,
+};
+
+use crate::{
+    assist_ctx::{ActionBuilder, Assist, AssistCtx},
+    auto_import_text_edit, AssistId, ImportsLocator,
+};
+
+// Assist: auto_import
+//
+// If the name is unresolved, provides all possible imports for it.
+//
+// ```
+// fn main() {
+//     let map = HashMap<|>::new();
+// }
+// ```
+// ->
+// ```
+// use std::collections::HashMap;
+//
+// fn main() {
+//     let map = HashMap<|>::new();
+// }
+// ```
+pub(crate) fn auto_import<F: ImportsLocator>(
+    ctx: AssistCtx<impl HirDatabase>,
+    imports_locator: &mut F,
+) -> Option<Assist> {
+    let path: ast::Path = ctx.find_node_at_offset()?;
+    let module = path.syntax().ancestors().find_map(ast::Module::cast);
+    let position = match module.and_then(|it| it.item_list()) {
+        Some(item_list) => item_list.syntax().clone(),
+        None => {
+            let current_file = path.syntax().ancestors().find_map(ast::SourceFile::cast)?;
+            current_file.syntax().clone()
+        }
+    };
+    let source_analyzer = ctx.source_analyzer(&position, None);
+    let module_with_name_to_import = source_analyzer.module()?;
+    let path_to_import = ctx.covering_element().ancestors().find_map(ast::Path::cast)?;
+    if source_analyzer.resolve_path(ctx.db, &path_to_import).is_some() {
+        return None;
+    }
+
+    let name_to_import = &find_applicable_name_ref(ctx.covering_element())?.syntax().to_string();
+    let proposed_imports = imports_locator
+        .find_imports(&name_to_import.to_string())
+        .into_iter()
+        .filter_map(|module_def| module_with_name_to_import.find_use_path(ctx.db, module_def))
+        .filter(|use_path| !use_path.segments.is_empty())
+        .take(20)
+        .map(|import| import.to_string())
+        .collect::<std::collections::BTreeSet<_>>();
+    if proposed_imports.is_empty() {
+        return None;
+    }
+
+    ctx.add_assist_group(AssistId("auto_import"), "auto import", || {
+        proposed_imports
+            .into_iter()
+            .map(|import| import_to_action(import, &position, &path_to_import.syntax()))
+            .collect()
+    })
+}
+
+fn find_applicable_name_ref(element: SyntaxElement) -> Option<ast::NameRef> {
+    if element.ancestors().find(|ancestor| ancestor.kind() == USE_ITEM).is_some() {
+        None
+    } else if element.kind() == NAME_REF {
+        Some(element.as_node().cloned().and_then(ast::NameRef::cast)?)
+    } else {
+        let parent = element.parent()?;
+        if parent.kind() == NAME_REF {
+            Some(ast::NameRef::cast(parent)?)
+        } else {
+            None
+        }
+    }
+}
+
+fn import_to_action(import: String, position: &SyntaxNode, anchor: &SyntaxNode) -> ActionBuilder {
+    let mut action_builder = ActionBuilder::default();
+    action_builder.label(format!("Import `{}`", &import));
+    auto_import_text_edit(
+        position,
+        anchor,
+        &[SmolStr::new(import)],
+        action_builder.text_edit_builder(),
+    );
+    action_builder
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::helpers::{
+        check_assist_with_imports_locator, check_assist_with_imports_locator_not_applicable,
+        TestImportsLocator,
+    };
+
+    #[test]
+    fn applicable_when_found_an_import() {
+        check_assist_with_imports_locator(
+            auto_import,
+            TestImportsLocator::new,
+            r"
+            PubStruct<|>
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+            r"
+            use PubMod::PubStruct;
+
+            PubStruct<|>
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn applicable_when_found_multiple_imports() {
+        check_assist_with_imports_locator(
+            auto_import,
+            TestImportsLocator::new,
+            r"
+            PubStruct<|>
+
+            pub mod PubMod1 {
+                pub struct PubStruct;
+            }
+            pub mod PubMod2 {
+                pub struct PubStruct;
+            }
+            pub mod PubMod3 {
+                pub struct PubStruct;
+            }
+            ",
+            r"
+            use PubMod1::PubStruct;
+
+            PubStruct<|>
+
+            pub mod PubMod1 {
+                pub struct PubStruct;
+            }
+            pub mod PubMod2 {
+                pub struct PubStruct;
+            }
+            pub mod PubMod3 {
+                pub struct PubStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_already_imported_types() {
+        check_assist_with_imports_locator_not_applicable(
+            auto_import,
+            TestImportsLocator::new,
+            r"
+            use PubMod::PubStruct;
+
+            PubStruct<|>
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_types_with_private_paths() {
+        check_assist_with_imports_locator_not_applicable(
+            auto_import,
+            TestImportsLocator::new,
+            r"
+            PrivateStruct<|>
+
+            pub mod PubMod {
+                struct PrivateStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_when_no_imports_found() {
+        check_assist_with_imports_locator_not_applicable(
+            auto_import,
+            TestImportsLocator::new,
+            "
+            PubStruct<|>",
+        );
+    }
+
+    #[test]
+    fn not_applicable_in_import_statements() {
+        check_assist_with_imports_locator_not_applicable(
+            auto_import,
+            TestImportsLocator::new,
+            r"
+            use PubStruct<|>;
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }",
+        );
+    }
+}
diff --git a/crates/ra_assists/src/assists/inline_local_variable.rs b/crates/ra_assists/src/assists/inline_local_variable.rs
index 45e0f983f..83527d904 100644
--- a/crates/ra_assists/src/assists/inline_local_variable.rs
+++ b/crates/ra_assists/src/assists/inline_local_variable.rs
@@ -23,7 +23,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     (1 + 2) * 4;
 // }
 // ```
-pub(crate) fn inline_local_varialbe(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn inline_local_variable(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let let_stmt = ctx.find_node_at_offset::<ast::LetStmt>()?;
     let bind_pat = match let_stmt.pat()? {
         ast::Pat::BindPat(pat) => pat,
@@ -47,6 +47,9 @@ pub(crate) fn inline_local_varialbe(ctx: AssistCtx<impl HirDatabase>) -> Option<
     };
     let analyzer = ctx.source_analyzer(bind_pat.syntax(), None);
     let refs = analyzer.find_all_refs(&bind_pat);
+    if refs.is_empty() {
+        return None;
+    };
 
     let mut wrap_in_parens = vec![true; refs.len()];
 
@@ -117,7 +120,7 @@ mod tests {
     #[test]
     fn test_inline_let_bind_literal_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn bar(a: usize) {}
 fn foo() {
@@ -151,7 +154,7 @@ fn foo() {
     #[test]
     fn test_inline_let_bind_bin_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn bar(a: usize) {}
 fn foo() {
@@ -185,7 +188,7 @@ fn foo() {
     #[test]
     fn test_inline_let_bind_function_call_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn bar(a: usize) {}
 fn foo() {
@@ -219,7 +222,7 @@ fn foo() {
     #[test]
     fn test_inline_let_bind_cast_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn bar(a: usize): usize { a }
 fn foo() {
@@ -253,7 +256,7 @@ fn foo() {
     #[test]
     fn test_inline_let_bind_block_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = { 10 + 1 };
@@ -285,7 +288,7 @@ fn foo() {
     #[test]
     fn test_inline_let_bind_paren_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = ( 10 + 1 );
@@ -317,7 +320,7 @@ fn foo() {
     #[test]
     fn test_not_inline_mut_variable() {
         check_assist_not_applicable(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let mut a<|> = 1 + 1;
@@ -329,7 +332,7 @@ fn foo() {
     #[test]
     fn test_call_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = bar(10 + 1);
@@ -347,7 +350,7 @@ fn foo() {
     #[test]
     fn test_index_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let x = vec![1, 2, 3];
@@ -367,7 +370,7 @@ fn foo() {
     #[test]
     fn test_method_call_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let bar = vec![1];
@@ -387,7 +390,7 @@ fn foo() {
     #[test]
     fn test_field_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 struct Bar {
     foo: usize
@@ -415,7 +418,7 @@ fn foo() {
     #[test]
     fn test_try_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() -> Option<usize> {
     let bar = Some(1);
@@ -437,7 +440,7 @@ fn foo() -> Option<usize> {
     #[test]
     fn test_ref_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let bar = 10;
@@ -455,7 +458,7 @@ fn foo() {
     #[test]
     fn test_tuple_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = (10, 20);
@@ -471,7 +474,7 @@ fn foo() {
     #[test]
     fn test_array_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = [1, 2, 3];
@@ -487,7 +490,7 @@ fn foo() {
     #[test]
     fn test_paren() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = (10 + 20);
@@ -505,7 +508,7 @@ fn foo() {
     #[test]
     fn test_path_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let d = 10;
@@ -525,7 +528,7 @@ fn foo() {
     #[test]
     fn test_block_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = { 10 };
@@ -543,7 +546,7 @@ fn foo() {
     #[test]
     fn test_used_in_different_expr1() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = 10 + 20;
@@ -565,7 +568,7 @@ fn foo() {
     #[test]
     fn test_used_in_for_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = vec![10, 20];
@@ -581,7 +584,7 @@ fn foo() {
     #[test]
     fn test_used_in_while_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = 1 > 0;
@@ -597,7 +600,7 @@ fn foo() {
     #[test]
     fn test_used_in_break_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = 1 + 1;
@@ -617,7 +620,7 @@ fn foo() {
     #[test]
     fn test_used_in_return_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = 1 > 0;
@@ -633,7 +636,7 @@ fn foo() {
     #[test]
     fn test_used_in_match_expr() {
         check_assist(
-            inline_local_varialbe,
+            inline_local_variable,
             "
 fn foo() {
     let a<|> = 1 > 0;
@@ -645,4 +648,16 @@ fn foo() {
 }",
         );
     }
+
+    #[test]
+    fn test_not_applicable_if_variable_unused() {
+        check_assist_not_applicable(
+            inline_local_variable,
+            "
+fn foo() {
+    let <|>a = 0;
+}
+            ",
+        )
+    }
 }
diff --git a/crates/ra_assists/src/doc_tests.rs b/crates/ra_assists/src/doc_tests.rs
index 5dc1ee233..65d51428b 100644
--- a/crates/ra_assists/src/doc_tests.rs
+++ b/crates/ra_assists/src/doc_tests.rs
@@ -11,6 +11,10 @@ use test_utils::{assert_eq_text, extract_range_or_offset};
 use crate::test_db::TestDB;
 
 fn check(assist_id: &str, before: &str, after: &str) {
+    // FIXME we cannot get the imports search functionality here yet, but still need to generate a test and a doc for an assist
+    if assist_id == "auto_import" {
+        return;
+    }
     let (selection, before) = extract_range_or_offset(before);
     let (db, file_id) = TestDB::with_single_file(&before);
     let frange = FileRange { file_id, range: selection.into() };
diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index 7d84dc8fb..ec4587ce7 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -215,6 +215,25 @@ fn main() {
 }
 
 #[test]
+fn doctest_auto_import() {
+    check(
+        "auto_import",
+        r#####"
+fn main() {
+    let map = HashMap<|>::new();
+}
+"#####,
+        r#####"
+use std::collections::HashMap;
+
+fn main() {
+    let map = HashMap<|>::new();
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_change_visibility() {
     check(
         "change_visibility",
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index d45b58966..625ebc4a2 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -14,7 +14,7 @@ mod test_db;
 pub mod ast_transform;
 
 use either::Either;
-use hir::db::HirDatabase;
+use hir::{db::HirDatabase, ModuleDef};
 use ra_db::FileRange;
 use ra_syntax::{TextRange, TextUnit};
 use ra_text_edit::TextEdit;
@@ -77,6 +77,51 @@ where
     })
 }
 
+/// A functionality for locating imports for the given name.
+///
+/// Currently has to be a trait with the real implementation provided by the ra_ide_api crate,
+/// due to the search functionality located there.
+/// Later, this trait should be removed completely and the search functionality moved to a separate crate,
+/// accessible from the ra_assists crate.
+pub trait ImportsLocator {
+    /// Finds all imports for the given name and the module that contains this name.
+    fn find_imports(&mut self, name_to_import: &str) -> Vec<ModuleDef>;
+}
+
+/// Return all the assists applicable at the given position
+/// and additional assists that need the imports locator functionality to work.
+///
+/// Assists are returned in the "resolved" state, that is with edit fully
+/// computed.
+pub fn assists_with_imports_locator<H, F>(
+    db: &H,
+    range: FileRange,
+    mut imports_locator: F,
+) -> Vec<ResolvedAssist>
+where
+    H: HirDatabase + 'static,
+    F: ImportsLocator,
+{
+    AssistCtx::with_ctx(db, range, true, |ctx| {
+        let mut assists = assists::all()
+            .iter()
+            .map(|f| f(ctx.clone()))
+            .chain(
+                assists::all_with_imports_locator()
+                    .iter()
+                    .map(|f| f(ctx.clone(), &mut imports_locator)),
+            )
+            .filter_map(std::convert::identity)
+            .map(|a| match a {
+                Assist::Resolved { assist } => assist,
+                Assist::Unresolved { .. } => unreachable!(),
+            })
+            .collect();
+        sort_assists(&mut assists);
+        assists
+    })
+}
+
 /// Return all the assists applicable at the given position.
 ///
 /// Assists are returned in the "resolved" state, that is with edit fully
@@ -85,8 +130,6 @@ pub fn assists<H>(db: &H, range: FileRange) -> Vec<ResolvedAssist>
 where
     H: HirDatabase + 'static,
 {
-    use std::cmp::Ordering;
-
     AssistCtx::with_ctx(db, range, true, |ctx| {
         let mut a = assists::all()
             .iter()
@@ -95,19 +138,24 @@ where
                 Assist::Resolved { assist } => assist,
                 Assist::Unresolved { .. } => unreachable!(),
             })
-            .collect::<Vec<_>>();
-        a.sort_by(|a, b| match (a.get_first_action().target, b.get_first_action().target) {
-            (Some(a), Some(b)) => a.len().cmp(&b.len()),
-            (Some(_), None) => Ordering::Less,
-            (None, Some(_)) => Ordering::Greater,
-            (None, None) => Ordering::Equal,
-        });
+            .collect();
+        sort_assists(&mut a);
         a
     })
 }
 
+fn sort_assists(assists: &mut Vec<ResolvedAssist>) {
+    use std::cmp::Ordering;
+    assists.sort_by(|a, b| match (a.get_first_action().target, b.get_first_action().target) {
+        (Some(a), Some(b)) => a.len().cmp(&b.len()),
+        (Some(_), None) => Ordering::Less,
+        (None, Some(_)) => Ordering::Greater,
+        (None, None) => Ordering::Equal,
+    });
+}
+
 mod assists {
-    use crate::{Assist, AssistCtx};
+    use crate::{Assist, AssistCtx, ImportsLocator};
     use hir::db::HirDatabase;
 
     mod add_derive;
@@ -116,6 +164,7 @@ mod assists {
     mod add_custom_impl;
     mod add_new;
     mod apply_demorgan;
+    mod auto_import;
     mod invert_if;
     mod flip_comma;
     mod flip_binexpr;
@@ -157,7 +206,7 @@ mod assists {
             add_import::add_import,
             add_missing_impl_members::add_missing_impl_members,
             add_missing_impl_members::add_missing_default_members,
-            inline_local_variable::inline_local_varialbe,
+            inline_local_variable::inline_local_variable,
             move_guard::move_guard_to_arm_body,
             move_guard::move_arm_cond_to_match_guard,
             move_bounds::move_bounds_to_where_clause,
@@ -168,15 +217,69 @@ mod assists {
             early_return::convert_to_guarded_return,
         ]
     }
+
+    pub(crate) fn all_with_imports_locator<'a, DB: HirDatabase, F: ImportsLocator>(
+    ) -> &'a [fn(AssistCtx<DB>, &mut F) -> Option<Assist>] {
+        &[auto_import::auto_import]
+    }
 }
 
 #[cfg(test)]
 mod helpers {
-    use ra_db::{fixture::WithFixture, FileRange};
+    use hir::db::DefDatabase;
+    use ra_db::{fixture::WithFixture, FileId, FileRange};
     use ra_syntax::TextRange;
     use test_utils::{add_cursor, assert_eq_text, extract_offset, extract_range};
 
-    use crate::{test_db::TestDB, Assist, AssistCtx};
+    use crate::{test_db::TestDB, Assist, AssistCtx, ImportsLocator};
+    use std::sync::Arc;
+
+    // FIXME remove the `ModuleDefId` reexport from `ra_hir` when this gets removed.
+    pub(crate) struct TestImportsLocator {
+        db: Arc<TestDB>,
+        test_file_id: FileId,
+    }
+
+    impl TestImportsLocator {
+        pub(crate) fn new(db: Arc<TestDB>, test_file_id: FileId) -> Self {
+            TestImportsLocator { db, test_file_id }
+        }
+    }
+
+    impl ImportsLocator for TestImportsLocator {
+        fn find_imports(&mut self, name_to_import: &str) -> Vec<hir::ModuleDef> {
+            let crate_def_map = self.db.crate_def_map(self.db.test_crate());
+            let mut findings = Vec::new();
+
+            let mut module_ids_to_process =
+                crate_def_map.modules_for_file(self.test_file_id).collect::<Vec<_>>();
+
+            while !module_ids_to_process.is_empty() {
+                let mut more_ids_to_process = Vec::new();
+                for local_module_id in module_ids_to_process.drain(..) {
+                    for (name, namespace_data) in
+                        crate_def_map[local_module_id].scope.entries_without_primitives()
+                    {
+                        let found_a_match = &name.to_string() == name_to_import;
+                        vec![namespace_data.types, namespace_data.values]
+                            .into_iter()
+                            .filter_map(std::convert::identity)
+                            .for_each(|(module_def_id, _)| {
+                                if found_a_match {
+                                    findings.push(module_def_id.into());
+                                }
+                                if let hir::ModuleDefId::ModuleId(module_id) = module_def_id {
+                                    more_ids_to_process.push(module_id.local_id);
+                                }
+                            });
+                    }
+                }
+                module_ids_to_process = more_ids_to_process;
+            }
+
+            findings
+        }
+    }
 
     pub(crate) fn check_assist(
         assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
@@ -206,6 +309,38 @@ mod helpers {
         assert_eq_text!(after, &actual);
     }
 
+    pub(crate) fn check_assist_with_imports_locator<F: ImportsLocator>(
+        assist: fn(AssistCtx<TestDB>, &mut F) -> Option<Assist>,
+        imports_locator_provider: fn(db: Arc<TestDB>, file_id: FileId) -> F,
+        before: &str,
+        after: &str,
+    ) {
+        let (before_cursor_pos, before) = extract_offset(before);
+        let (db, file_id) = TestDB::with_single_file(&before);
+        let db = Arc::new(db);
+        let mut imports_locator = imports_locator_provider(Arc::clone(&db), file_id);
+        let frange =
+            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
+        let assist =
+            AssistCtx::with_ctx(db.as_ref(), frange, true, |ctx| assist(ctx, &mut imports_locator))
+                .expect("code action is not applicable");
+        let action = match assist {
+            Assist::Unresolved { .. } => unreachable!(),
+            Assist::Resolved { assist } => assist.get_first_action(),
+        };
+
+        let actual = action.edit.apply(&before);
+        let actual_cursor_pos = match action.cursor_position {
+            None => action
+                .edit
+                .apply_to_offset(before_cursor_pos)
+                .expect("cursor position is affected by the edit"),
+            Some(off) => off,
+        };
+        let actual = add_cursor(&actual, actual_cursor_pos);
+        assert_eq_text!(after, &actual);
+    }
+
     pub(crate) fn check_assist_range(
         assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
         before: &str,
@@ -279,6 +414,22 @@ mod helpers {
         assert!(assist.is_none());
     }
 
+    pub(crate) fn check_assist_with_imports_locator_not_applicable<F: ImportsLocator>(
+        assist: fn(AssistCtx<TestDB>, &mut F) -> Option<Assist>,
+        imports_locator_provider: fn(db: Arc<TestDB>, file_id: FileId) -> F,
+        before: &str,
+    ) {
+        let (before_cursor_pos, before) = extract_offset(before);
+        let (db, file_id) = TestDB::with_single_file(&before);
+        let db = Arc::new(db);
+        let mut imports_locator = imports_locator_provider(Arc::clone(&db), file_id);
+        let frange =
+            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
+        let assist =
+            AssistCtx::with_ctx(db.as_ref(), frange, true, |ctx| assist(ctx, &mut imports_locator));
+        assert!(assist.is_none());
+    }
+
     pub(crate) fn check_assist_range_not_applicable(
         assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
         before: &str,
diff --git a/crates/ra_cargo_watch/Cargo.toml b/crates/ra_cargo_watch/Cargo.toml
index 9ead48abf..49e06e0d3 100644
--- a/crates/ra_cargo_watch/Cargo.toml
+++ b/crates/ra_cargo_watch/Cargo.toml
@@ -6,12 +6,12 @@ authors = ["rust-analyzer developers"]
 
 [dependencies]
 crossbeam-channel = "0.4"
-lsp-types = { version = "0.69.0", features = ["proposed"] }
+lsp-types = { version = "0.70.0", features = ["proposed"] }
 log = "0.4.3"
 cargo_metadata = "0.9.1"
 jod-thread = "0.1.0"
 parking_lot = "0.10.0"
 
 [dev-dependencies]
-insta = "0.12.0"
+insta = "0.13.0"
 serde_json = "1.0"
\ No newline at end of file
diff --git a/crates/ra_cargo_watch/src/conv.rs b/crates/ra_cargo_watch/src/conv.rs
index ac0f1d28a..8fba400ae 100644
--- a/crates/ra_cargo_watch/src/conv.rs
+++ b/crates/ra_cargo_watch/src/conv.rs
@@ -117,7 +117,7 @@ fn is_deprecated(rd: &RustDiagnostic) -> bool {
     }
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct SuggestedFix {
     pub title: String,
     pub location: Location,
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_clippy_pass_by_ref.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
index cb0920914..cb0920914 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_clippy_pass_by_ref.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_handles_macro_location.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_handles_macro_location.snap
index 19510ecc1..19510ecc1 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_handles_macro_location.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_handles_macro_location.snap
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_macro_compiler_error.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_macro_compiler_error.snap
index 92f7eec05..92f7eec05 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_macro_compiler_error.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_macro_compiler_error.snap
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_rustc_incompatible_type_for_trait.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_incompatible_type_for_trait.snap
index cf683e4b6..cf683e4b6 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_rustc_incompatible_type_for_trait.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_incompatible_type_for_trait.snap
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_rustc_mismatched_type.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_mismatched_type.snap
index 8c1483c74..8c1483c74 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_rustc_mismatched_type.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_mismatched_type.snap
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_rustc_unused_variable.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_unused_variable.snap
index eb5a2247b..eb5a2247b 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_rustc_unused_variable.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_unused_variable.snap
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_rustc_wrong_number_of_parameters.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_wrong_number_of_parameters.snap
index 2f4518931..2f4518931 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/test__snap_rustc_wrong_number_of_parameters.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_wrong_number_of_parameters.snap
diff --git a/crates/ra_cargo_watch/src/lib.rs b/crates/ra_cargo_watch/src/lib.rs
index 7f4c9280c..bbe634603 100644
--- a/crates/ra_cargo_watch/src/lib.rs
+++ b/crates/ra_cargo_watch/src/lib.rs
@@ -7,7 +7,6 @@ use lsp_types::{
     Diagnostic, Url, WorkDoneProgress, WorkDoneProgressBegin, WorkDoneProgressEnd,
     WorkDoneProgressReport,
 };
-use parking_lot::RwLock;
 use std::{
     collections::HashMap,
     path::PathBuf,
@@ -38,7 +37,7 @@ pub struct CheckOptions {
 #[derive(Debug)]
 pub struct CheckWatcher {
     pub task_recv: Receiver<CheckTask>,
-    pub state: Arc<RwLock<CheckState>>,
+    pub state: Arc<CheckState>,
     cmd_send: Option<Sender<CheckCommand>>,
     handle: Option<JoinHandle<()>>,
 }
@@ -46,7 +45,7 @@ pub struct CheckWatcher {
 impl CheckWatcher {
     pub fn new(options: &CheckOptions, workspace_root: PathBuf) -> CheckWatcher {
         let options = options.clone();
-        let state = Arc::new(RwLock::new(CheckState::new()));
+        let state = Arc::new(CheckState::new());
 
         let (task_send, task_recv) = unbounded::<CheckTask>();
         let (cmd_send, cmd_recv) = unbounded::<CheckCommand>();
@@ -59,7 +58,7 @@ impl CheckWatcher {
 
     /// Returns a CheckWatcher that doesn't actually do anything
     pub fn dummy() -> CheckWatcher {
-        let state = Arc::new(RwLock::new(CheckState::new()));
+        let state = Arc::new(CheckState::new());
         CheckWatcher { task_recv: never(), cmd_send: None, handle: None, state }
     }
 
@@ -87,7 +86,7 @@ impl std::ops::Drop for CheckWatcher {
     }
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct CheckState {
     diagnostic_collection: HashMap<Url, Vec<Diagnostic>>,
     suggested_fix_collection: HashMap<Url, Vec<SuggestedFix>>,
diff --git a/crates/ra_cli/Cargo.toml b/crates/ra_cli/Cargo.toml
index 12af075f7..bcd408421 100644
--- a/crates/ra_cli/Cargo.toml
+++ b/crates/ra_cli/Cargo.toml
@@ -7,7 +7,7 @@ publish = false
 
 [dependencies]
 pico-args = "0.3.0"
-env_logger = { version = "0.7.1", default-features = false, features = ["humantime"] }
+env_logger = { version = "0.7.1", default-features = false }
 
 ra_syntax = { path = "../ra_syntax" }
 ra_ide = { path = "../ra_ide" }
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index e1c7b7a20..9e2673d13 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -56,6 +56,7 @@ pub use hir_def::{
     nameres::ModuleSource,
     path::{ModPath, Path, PathKind},
     type_ref::Mutability,
+    ModuleDefId, // FIXME this is exposed and should be used for implementing the `TestImportsLocator` in `ra_assists` only, should be removed later along with the trait and the implementation.
 };
 pub use hir_expand::{
     name::Name, HirFileId, InFile, MacroCallId, MacroCallLoc, MacroDefId, MacroFile, Origin,
diff --git a/crates/ra_hir_def/Cargo.toml b/crates/ra_hir_def/Cargo.toml
index 2c368f690..1efa00fe0 100644
--- a/crates/ra_hir_def/Cargo.toml
+++ b/crates/ra_hir_def/Cargo.toml
@@ -26,4 +26,4 @@ ra_cfg = { path = "../ra_cfg" }
 tt = { path = "../ra_tt", package = "ra_tt" }
 
 [dev-dependencies]
-insta = "0.12.0"
+insta = "0.13.0"
diff --git a/crates/ra_hir_ty/Cargo.toml b/crates/ra_hir_ty/Cargo.toml
index 60793db44..d229639d9 100644
--- a/crates/ra_hir_ty/Cargo.toml
+++ b/crates/ra_hir_ty/Cargo.toml
@@ -28,4 +28,4 @@ chalk-ir =      { git = "https://github.com/rust-lang/chalk.git", rev = "ff65b5a
 lalrpop-intern = "0.15.1"
 
 [dev-dependencies]
-insta = "0.12.0"
+insta = "0.13.0"
diff --git a/crates/ra_hir_ty/src/display.rs b/crates/ra_hir_ty/src/display.rs
index 37def7c03..d1ff85f0f 100644
--- a/crates/ra_hir_ty/src/display.rs
+++ b/crates/ra_hir_ty/src/display.rs
@@ -9,7 +9,7 @@ pub struct HirFormatter<'a, 'b, DB> {
     fmt: &'a mut fmt::Formatter<'b>,
     buf: String,
     curr_size: usize,
-    max_size: Option<usize>,
+    pub(crate) max_size: Option<usize>,
     omit_verbose_types: bool,
 }
 
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index d63f862dc..908e4862d 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -855,7 +855,12 @@ impl HirDisplay for ApplicationTy {
             }
             TypeCtor::Ref(m) => {
                 let t = self.parameters.as_single();
-                write!(f, "&{}{}", m.as_keyword_for_ref(), t.display(f.db))?;
+                let ty_display = if f.omit_verbose_types() {
+                    t.display_truncated(f.db, f.max_size)
+                } else {
+                    t.display(f.db)
+                };
+                write!(f, "&{}{}", m.as_keyword_for_ref(), ty_display)?;
             }
             TypeCtor::Never => write!(f, "!")?,
             TypeCtor::Tuple { .. } => {
diff --git a/crates/ra_ide/Cargo.toml b/crates/ra_ide/Cargo.toml
index 2c9f9dce0..53817d1f7 100644
--- a/crates/ra_ide/Cargo.toml
+++ b/crates/ra_ide/Cargo.toml
@@ -39,7 +39,7 @@ ra_assists = { path = "../ra_assists" }
 hir = { path = "../ra_hir", package = "ra_hir" }
 
 [dev-dependencies]
-insta = "0.12.0"
+insta = "0.13.0"
 
 [dev-dependencies.proptest]
 version = "0.9.0"
diff --git a/crates/ra_ide/src/assists.rs b/crates/ra_ide/src/assists.rs
index a936900da..c43c45c65 100644
--- a/crates/ra_ide/src/assists.rs
+++ b/crates/ra_ide/src/assists.rs
@@ -2,8 +2,9 @@
 
 use ra_db::{FilePosition, FileRange};
 
-use crate::{db::RootDatabase, FileId, SourceChange, SourceFileEdit};
-
+use crate::{
+    db::RootDatabase, imports_locator::ImportsLocatorIde, FileId, SourceChange, SourceFileEdit,
+};
 use either::Either;
 pub use ra_assists::AssistId;
 use ra_assists::{AssistAction, AssistLabel};
@@ -16,7 +17,7 @@ pub struct Assist {
 }
 
 pub(crate) fn assists(db: &RootDatabase, frange: FileRange) -> Vec<Assist> {
-    ra_assists::assists(db, frange)
+    ra_assists::assists_with_imports_locator(db, frange, ImportsLocatorIde::new(db))
         .into_iter()
         .map(|assist| {
             let file_id = frange.file_id;
diff --git a/crates/ra_ide/src/change.rs b/crates/ra_ide/src/change.rs
index b0aa2c8e0..ce617840c 100644
--- a/crates/ra_ide/src/change.rs
+++ b/crates/ra_ide/src/change.rs
@@ -166,13 +166,15 @@ impl LibraryData {
 const GC_COOLDOWN: time::Duration = time::Duration::from_millis(100);
 
 impl RootDatabase {
+    pub(crate) fn request_cancellation(&mut self) {
+        let _p = profile("RootDatabase::request_cancellation");
+        self.salsa_runtime_mut().synthetic_write(Durability::LOW);
+    }
+
     pub(crate) fn apply_change(&mut self, change: AnalysisChange) {
         let _p = profile("RootDatabase::apply_change");
+        self.request_cancellation();
         log::info!("apply_change {:?}", change);
-        {
-            let _p = profile("RootDatabase::apply_change/cancellation");
-            self.salsa_runtime_mut().synthetic_write(Durability::LOW);
-        }
         if !change.new_roots.is_empty() {
             let mut local_roots = Vec::clone(&self.local_roots());
             for (root_id, is_local) in change.new_roots {
diff --git a/crates/ra_ide/src/imports_locator.rs b/crates/ra_ide/src/imports_locator.rs
new file mode 100644
index 000000000..48b014c7d
--- /dev/null
+++ b/crates/ra_ide/src/imports_locator.rs
@@ -0,0 +1,76 @@
+//! This module contains an import search funcionality that is provided to the ra_assists module.
+//! Later, this should be moved away to a separate crate that is accessible from the ra_assists module.
+
+use crate::{
+    db::RootDatabase,
+    references::{classify_name, NameDefinition, NameKind},
+    symbol_index::{self, FileSymbol},
+    Query,
+};
+use hir::{db::HirDatabase, ModuleDef, SourceBinder};
+use ra_assists::ImportsLocator;
+use ra_prof::profile;
+use ra_syntax::{ast, AstNode, SyntaxKind::NAME};
+
+pub(crate) struct ImportsLocatorIde<'a> {
+    source_binder: SourceBinder<'a, RootDatabase>,
+}
+
+impl<'a> ImportsLocatorIde<'a> {
+    pub(crate) fn new(db: &'a RootDatabase) -> Self {
+        Self { source_binder: SourceBinder::new(db) }
+    }
+
+    fn get_name_definition(
+        &mut self,
+        db: &impl HirDatabase,
+        import_candidate: &FileSymbol,
+    ) -> Option<NameDefinition> {
+        let _p = profile("get_name_definition");
+        let file_id = import_candidate.file_id.into();
+        let candidate_node = import_candidate.ptr.to_node(&db.parse_or_expand(file_id)?);
+        let candidate_name_node = if candidate_node.kind() != NAME {
+            candidate_node.children().find(|it| it.kind() == NAME)?
+        } else {
+            candidate_node
+        };
+        classify_name(
+            &mut self.source_binder,
+            hir::InFile { file_id, value: &ast::Name::cast(candidate_name_node)? },
+        )
+    }
+}
+
+impl ImportsLocator for ImportsLocatorIde<'_> {
+    fn find_imports(&mut self, name_to_import: &str) -> Vec<ModuleDef> {
+        let _p = profile("search_for_imports");
+        let db = self.source_binder.db;
+
+        let project_results = {
+            let mut query = Query::new(name_to_import.to_string());
+            query.exact();
+            query.limit(40);
+            symbol_index::world_symbols(db, query)
+        };
+        let lib_results = {
+            let mut query = Query::new(name_to_import.to_string());
+            query.libs();
+            query.exact();
+            query.limit(40);
+            symbol_index::world_symbols(db, query)
+        };
+
+        project_results
+            .into_iter()
+            .chain(lib_results.into_iter())
+            .filter_map(|import_candidate| self.get_name_definition(db, &import_candidate))
+            .filter_map(|name_definition_to_import| {
+                if let NameKind::Def(module_def) = name_definition_to_import.kind {
+                    Some(module_def)
+                } else {
+                    None
+                }
+            })
+            .collect()
+    }
+}
diff --git a/crates/ra_ide/src/inlay_hints.rs b/crates/ra_ide/src/inlay_hints.rs
index 236557541..393ca9447 100644
--- a/crates/ra_ide/src/inlay_hints.rs
+++ b/crates/ra_ide/src/inlay_hints.rs
@@ -245,6 +245,7 @@ struct Test<K, T = u8> {
 
 fn main() {
     let zz = Test { t: 23, k: 33 };
+    let zz_ref = &zz;
 }"#,
         );
 
@@ -255,6 +256,11 @@ fn main() {
                 kind: TypeHint,
                 label: "Test<i32>",
             },
+            InlayHint {
+                range: [105; 111),
+                kind: TypeHint,
+                label: "&Test<i32>",
+            },
         ]
         "###
         );
@@ -374,6 +380,7 @@ fn main() {
 
     let multiply = |a, b, c, d| a * b * c * d;
     let _: i32 = multiply(1, 2, 3, 4);
+    let multiply_ref = &multiply;
 
     let return_42 = || 42;
 }"#,
@@ -417,7 +424,12 @@ fn main() {
                 label: "i32",
             },
             InlayHint {
-                range: [201; 210),
+                range: [200; 212),
+                kind: TypeHint,
+                label: "&|…| -> i32",
+            },
+            InlayHint {
+                range: [235; 244),
                 kind: TypeHint,
                 label: "|| -> i32",
             },
diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index 4d8deb21c..03ad6b2c1 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -30,6 +30,7 @@ mod syntax_highlighting;
 mod parent_module;
 mod references;
 mod impls;
+mod imports_locator;
 mod assists;
 mod diagnostics;
 mod syntax_tree;
@@ -202,6 +203,9 @@ impl AnalysisHost {
     pub fn per_query_memory_usage(&mut self) -> Vec<(String, ra_prof::Bytes)> {
         self.db.per_query_memory_usage()
     }
+    pub fn request_cancellation(&mut self) {
+        self.db.request_cancellation();
+    }
     pub fn raw_database(
         &self,
     ) -> &(impl hir::db::HirDatabase + salsa::Database + ra_db::SourceDatabaseExt) {
diff --git a/crates/ra_ide/src/runnables.rs b/crates/ra_ide/src/runnables.rs
index 7533692f6..8622dd956 100644
--- a/crates/ra_ide/src/runnables.rs
+++ b/crates/ra_ide/src/runnables.rs
@@ -43,7 +43,7 @@ fn runnable_fn(fn_def: ast::FnDef) -> Option<Runnable> {
     let name = fn_def.name()?.text().clone();
     let kind = if name == "main" {
         RunnableKind::Bin
-    } else if fn_def.has_atom_attr("test") {
+    } else if has_test_related_attribute(&fn_def) {
         RunnableKind::Test { name: name.to_string() }
     } else if fn_def.has_atom_attr("bench") {
         RunnableKind::Bench { name: name.to_string() }
@@ -53,6 +53,20 @@ fn runnable_fn(fn_def: ast::FnDef) -> Option<Runnable> {
     Some(Runnable { range: fn_def.syntax().text_range(), kind })
 }
 
+/// This is a method with a heuristics to support test methods annotated with custom test annotations, such as
+/// `#[test_case(...)]`, `#[tokio::test]` and similar.
+/// Also a regular `#[test]` annotation is supported.
+///
+/// It may produce false positives, for example, `#[wasm_bindgen_test]` requires a different command to run the test,
+/// but it's better than not to have the runnables for the tests at all.
+fn has_test_related_attribute(fn_def: &ast::FnDef) -> bool {
+    fn_def
+        .attrs()
+        .filter_map(|attr| attr.path())
+        .map(|path| path.syntax().to_string().to_lowercase())
+        .any(|attribute_text| attribute_text.contains("test"))
+}
+
 fn runnable_mod(db: &RootDatabase, file_id: FileId, module: ast::Module) -> Option<Runnable> {
     let has_test_function = module
         .item_list()?
diff --git a/crates/ra_lsp_server/Cargo.toml b/crates/ra_lsp_server/Cargo.toml
index 579158780..fdf81ed87 100644
--- a/crates/ra_lsp_server/Cargo.toml
+++ b/crates/ra_lsp_server/Cargo.toml
@@ -14,7 +14,7 @@ serde_json = "1.0.34"
 serde = { version = "1.0.83", features = ["derive"] }
 crossbeam-channel = "0.4"
 log = "0.4.3"
-lsp-types = { version = "0.69.0", features = ["proposed"] }
+lsp-types = { version = "0.70.0", features = ["proposed"] }
 rustc-hash = "1.0"
 parking_lot = "0.10.0"
 jod-thread = "0.1.0"
@@ -26,10 +26,13 @@ lsp-server = "0.3.0"
 ra_project_model = { path = "../ra_project_model" }
 ra_prof = { path = "../ra_prof" }
 ra_vfs_glob = { path = "../ra_vfs_glob" }
-env_logger = { version = "0.7.1", default-features = false, features = ["humantime"] }
+env_logger = { version = "0.7.1", default-features = false }
 ra_cargo_watch = { path = "../ra_cargo_watch" }
 either = "1.5"
 
+[target.'cfg(windows)'.dependencies]
+winapi = "0.3"
+
 [dev-dependencies]
 tempfile = "3"
 test_utils = { path = "../test_utils" }
diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 7822be2e2..15bf519c9 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -29,9 +29,6 @@ use crate::{
     Result, ServerConfig,
 };
 
-const THREADPOOL_SIZE: usize = 8;
-const MAX_IN_FLIGHT_LIBS: usize = THREADPOOL_SIZE - 3;
-
 #[derive(Debug)]
 pub struct LspError {
     pub code: i32,
@@ -60,6 +57,25 @@ pub fn main_loop(
 ) -> Result<()> {
     log::info!("server_config: {:#?}", config);
 
+    // Windows scheduler implements priority boosts: if thread waits for an
+    // event (like a condvar), and event fires, priority of the thread is
+    // temporary bumped. This optimization backfires in our case: each time the
+    // `main_loop` schedules a task to run on a threadpool, the worker threads
+    // gets a higher priority, and (on a machine with fewer cores) displaces the
+    // main loop! We work-around this by marking the main loop as a
+    // higher-priority thread.
+    //
+    // https://docs.microsoft.com/en-us/windows/win32/procthread/scheduling-priorities
+    // https://docs.microsoft.com/en-us/windows/win32/procthread/priority-boosts
+    // https://github.com/rust-analyzer/rust-analyzer/issues/2835
+    #[cfg(windows)]
+    unsafe {
+        use winapi::um::processthreadsapi::*;
+        let thread = GetCurrentThread();
+        let thread_priority_above_normal = 1;
+        SetThreadPriority(thread, thread_priority_above_normal);
+    }
+
     let mut loop_state = LoopState::default();
     let mut world_state = {
         let feature_flags = {
@@ -168,7 +184,7 @@ pub fn main_loop(
         )
     };
 
-    let pool = ThreadPool::new(THREADPOOL_SIZE);
+    let pool = ThreadPool::default();
     let (task_sender, task_receiver) = unbounded::<Task>();
     let (libdata_sender, libdata_receiver) = unbounded::<LibraryData>();
 
@@ -210,7 +226,7 @@ pub fn main_loop(
             )?;
         }
     }
-
+    world_state.analysis_host.request_cancellation();
     log::info!("waiting for tasks to finish...");
     task_receiver.into_iter().for_each(|task| {
         on_task(task, &connection.sender, &mut loop_state.pending_requests, &mut world_state)
@@ -371,7 +387,8 @@ fn loop_turn(
         loop_state.pending_libraries.extend(changes);
     }
 
-    while loop_state.in_flight_libraries < MAX_IN_FLIGHT_LIBS
+    let max_in_flight_libs = pool.max_count().saturating_sub(2).max(1);
+    while loop_state.in_flight_libraries < max_in_flight_libs
         && !loop_state.pending_libraries.is_empty()
     {
         let (root, files) = loop_state.pending_libraries.pop().unwrap();
@@ -586,12 +603,14 @@ fn on_notification(
 
 fn on_check_task(
     task: CheckTask,
-    world_state: &WorldState,
+    world_state: &mut WorldState,
     task_sender: &Sender<Task>,
 ) -> Result<()> {
     match task {
         CheckTask::ClearDiagnostics => {
-            let cleared_files = world_state.check_watcher.state.write().clear();
+            let state = Arc::get_mut(&mut world_state.check_watcher.state)
+                .expect("couldn't get check watcher state as mutable");
+            let cleared_files = state.clear();
 
             // Send updated diagnostics for each cleared file
             for url in cleared_files {
@@ -600,11 +619,9 @@ fn on_check_task(
         }
 
         CheckTask::AddDiagnostic(url, diagnostic) => {
-            world_state
-                .check_watcher
-                .state
-                .write()
-                .add_diagnostic_with_fixes(url.clone(), diagnostic);
+            let state = Arc::get_mut(&mut world_state.check_watcher.state)
+                .expect("couldn't get check watcher state as mutable");
+            state.add_diagnostic_with_fixes(url.clone(), diagnostic);
 
             // We manually send a diagnostic update when the watcher asks
             // us to, to avoid the issue of having to change the file to
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 8e43f0575..666f2ee29 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -674,8 +674,7 @@ pub fn handle_code_action(
         res.push(action.into());
     }
 
-    for fix in world.check_watcher.read().fixes_for(&params.text_document.uri).into_iter().flatten()
-    {
+    for fix in world.check_watcher.fixes_for(&params.text_document.uri).into_iter().flatten() {
         let fix_range = fix.location.range.conv_with(&line_index);
         if fix_range.intersection(&range).is_none() {
             continue;
@@ -895,7 +894,7 @@ pub fn publish_diagnostics(
             tags: None,
         })
         .collect();
-    if let Some(check_diags) = world.check_watcher.read().diagnostics_for(&uri) {
+    if let Some(check_diags) = world.check_watcher.diagnostics_for(&uri) {
         diagnostics.extend(check_diags.iter().cloned());
     }
     Ok(req::PublishDiagnosticsParams { uri, diagnostics, version: None })
diff --git a/crates/ra_lsp_server/src/world.rs b/crates/ra_lsp_server/src/world.rs
index e7a0acfc7..3059ef9ec 100644
--- a/crates/ra_lsp_server/src/world.rs
+++ b/crates/ra_lsp_server/src/world.rs
@@ -63,7 +63,7 @@ pub struct WorldSnapshot {
     pub workspaces: Arc<Vec<ProjectWorkspace>>,
     pub analysis: Analysis,
     pub latest_requests: Arc<RwLock<LatestRequests>>,
-    pub check_watcher: Arc<RwLock<CheckState>>,
+    pub check_watcher: CheckState,
     vfs: Arc<RwLock<Vfs>>,
 }
 
@@ -220,7 +220,7 @@ impl WorldState {
             analysis: self.analysis_host.analysis(),
             vfs: Arc::clone(&self.vfs),
             latest_requests: Arc::clone(&self.latest_requests),
-            check_watcher: self.check_watcher.state.clone(),
+            check_watcher: (*self.check_watcher.state).clone(),
         }
     }
 
diff --git a/crates/ra_parser/src/lib.rs b/crates/ra_parser/src/lib.rs
index 65134277e..81055746b 100644
--- a/crates/ra_parser/src/lib.rs
+++ b/crates/ra_parser/src/lib.rs
@@ -27,7 +27,7 @@ pub use syntax_kind::SyntaxKind;
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct ParseError(pub String);
 
-/// `TokenSource` abstracts the source of the tokens parser operates one.
+/// `TokenSource` abstracts the source of the tokens parser operates on.
 ///
 /// Hopefully this will allow us to treat text and token trees in the same way!
 pub trait TokenSource {
@@ -43,7 +43,7 @@ pub trait TokenSource {
     fn is_keyword(&self, kw: &str) -> bool;
 }
 
-/// `TokenCursor` abstracts the cursor of `TokenSource` operates one.
+/// `Token` abstracts the cursor of `TokenSource` operates on.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub struct Token {
     /// What is the current token?
diff --git a/crates/ra_prof/src/lib.rs b/crates/ra_prof/src/lib.rs
index da541005a..c7973ddf4 100644
--- a/crates/ra_prof/src/lib.rs
+++ b/crates/ra_prof/src/lib.rs
@@ -106,6 +106,21 @@ pub fn profile(desc: &str) -> Profiler {
     })
 }
 
+pub fn print_time(desc: &str) -> impl Drop + '_ {
+    struct Guard<'a> {
+        desc: &'a str,
+        start: Instant,
+    }
+
+    impl Drop for Guard<'_> {
+        fn drop(&mut self) {
+            eprintln!("{}: {:?}", self.desc, self.start.elapsed())
+        }
+    }
+
+    Guard { desc, start: Instant::now() }
+}
+
 pub struct Profiler {
     desc: Option<String>,
 }
diff --git a/crates/ra_syntax/src/ast/expr_extensions.rs b/crates/ra_syntax/src/ast/expr_extensions.rs
index 6da4b1309..539759450 100644
--- a/crates/ra_syntax/src/ast/expr_extensions.rs
+++ b/crates/ra_syntax/src/ast/expr_extensions.rs
@@ -305,44 +305,39 @@ impl ast::Literal {
             .unwrap()
     }
 
+    fn find_suffix(text: &str, possible_suffixes: &[&str]) -> Option<SmolStr> {
+        possible_suffixes
+            .iter()
+            .find(|&suffix| text.ends_with(suffix))
+            .map(|&suffix| SmolStr::new(suffix))
+    }
+
     pub fn kind(&self) -> LiteralKind {
-        match self.token().kind() {
-            INT_NUMBER => {
-                let int_suffix_list = [
-                    "isize", "i128", "i64", "i32", "i16", "i8", "usize", "u128", "u64", "u32",
-                    "u16", "u8",
-                ];
+        const INT_SUFFIXES: [&'static str; 12] = [
+            "u64", "u32", "u16", "u8", "usize", "isize", "i64", "i32", "i16", "i8", "u128", "i128",
+        ];
+        const FLOAT_SUFFIXES: [&'static str; 2] = ["f32", "f64"];
 
+        let token = self.token();
+
+        match token.kind() {
+            INT_NUMBER => {
+                // FYI: there was a bug here previously, thus an if statement bellow is necessary.
                 // The lexer treats e.g. `1f64` as an integer literal. See
                 // https://github.com/rust-analyzer/rust-analyzer/issues/1592
                 // and the comments on the linked PR.
-                let float_suffix_list = ["f32", "f64"];
-
-                let text = self.token().text().to_string();
 
-                let float_suffix = float_suffix_list
-                    .iter()
-                    .find(|&s| text.ends_with(s))
-                    .map(|&suf| SmolStr::new(suf));
+                let text = token.text();
 
-                if float_suffix.is_some() {
-                    LiteralKind::FloatNumber { suffix: float_suffix }
+                if let suffix @ Some(_) = Self::find_suffix(&text, &FLOAT_SUFFIXES) {
+                    LiteralKind::FloatNumber { suffix }
                 } else {
-                    let suffix = int_suffix_list
-                        .iter()
-                        .find(|&s| text.ends_with(s))
-                        .map(|&suf| SmolStr::new(suf));
-                    LiteralKind::IntNumber { suffix }
+                    LiteralKind::IntNumber { suffix: Self::find_suffix(&text, &INT_SUFFIXES) }
                 }
             }
             FLOAT_NUMBER => {
-                let allowed_suffix_list = ["f64", "f32"];
-                let text = self.token().text().to_string();
-                let suffix = allowed_suffix_list
-                    .iter()
-                    .find(|&s| text.ends_with(s))
-                    .map(|&suf| SmolStr::new(suf));
-                LiteralKind::FloatNumber { suffix }
+                let text = token.text();
+                LiteralKind::FloatNumber { suffix: Self::find_suffix(&text, &FLOAT_SUFFIXES) }
             }
             STRING | RAW_STRING => LiteralKind::String,
             T![true] | T![false] => LiteralKind::Bool,
diff --git a/crates/ra_syntax/src/ast/extensions.rs b/crates/ra_syntax/src/ast/extensions.rs
index d9666cdca..cb0aee422 100644
--- a/crates/ra_syntax/src/ast/extensions.rs
+++ b/crates/ra_syntax/src/ast/extensions.rs
@@ -234,6 +234,10 @@ impl ast::LetStmt {
             Some(node) => node.kind() == T![;],
         }
     }
+
+    pub fn eq_token(&self) -> Option<SyntaxToken> {
+        self.syntax().children_with_tokens().find(|t| t.kind() == EQ).and_then(|it| it.into_token())
+    }
 }
 
 impl ast::ExprStmt {