19 files changed, 505 insertions, 315 deletions

diff --git a/crates/ra_assists/src/assists/auto_import.rs b/crates/ra_assists/src/assists/auto_import.rs
index 9163cc662..69126a1c9 100644
--- a/crates/ra_assists/src/assists/auto_import.rs
+++ b/crates/ra_assists/src/assists/auto_import.rs
@@ -1,8 +1,8 @@
 use hir::db::HirDatabase;
 use ra_syntax::{
     ast::{self, AstNode},
-    SmolStr, SyntaxElement,
-    SyntaxKind::{NAME_REF, USE_ITEM},
+    SmolStr,
+    SyntaxKind::USE_ITEM,
     SyntaxNode,
 };
 
@@ -32,25 +32,28 @@ 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 path_to_import: ast::Path = ctx.find_node_at_offset()?;
+    let path_to_import_syntax = path_to_import.syntax();
+    if path_to_import_syntax.ancestors().find(|ancestor| ancestor.kind() == USE_ITEM).is_some() {
+        return None;
+    }
+
+    let module = path_to_import_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)?;
+            let current_file = path_to_import_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())
+        .find_imports(&path_to_import_syntax.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())
@@ -64,26 +67,11 @@ pub(crate) fn auto_import<F: ImportsLocator>(
     ctx.add_assist_group(AssistId("auto_import"), "auto import", || {
         proposed_imports
             .into_iter()
-            .map(|import| import_to_action(import, &position, &path_to_import.syntax()))
+            .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));
@@ -110,16 +98,16 @@ mod tests {
             auto_import,
             TestImportsLocator::new,
             r"
-            PubStruct<|>
+            <|>PubStruct
 
             pub mod PubMod {
                 pub struct PubStruct;
             }
             ",
             r"
-            use PubMod::PubStruct;
+            <|>use PubMod::PubStruct;
 
-            PubStruct<|>
+            PubStruct
 
             pub mod PubMod {
                 pub struct PubStruct;
@@ -134,7 +122,7 @@ mod tests {
             auto_import,
             TestImportsLocator::new,
             r"
-            PubStruct<|>
+            PubSt<|>ruct
 
             pub mod PubMod1 {
                 pub struct PubStruct;
@@ -149,7 +137,7 @@ mod tests {
             r"
             use PubMod1::PubStruct;
 
-            PubStruct<|>
+            PubSt<|>ruct
 
             pub mod PubMod1 {
                 pub struct PubStruct;
diff --git a/crates/ra_cargo_watch/Cargo.toml b/crates/ra_cargo_watch/Cargo.toml
index 49e06e0d3..dd814fc9d 100644
--- a/crates/ra_cargo_watch/Cargo.toml
+++ b/crates/ra_cargo_watch/Cargo.toml
@@ -11,6 +11,7 @@ log = "0.4.3"
 cargo_metadata = "0.9.1"
 jod-thread = "0.1.0"
 parking_lot = "0.10.0"
+serde_json = "1.0.45"
 
 [dev-dependencies]
 insta = "0.13.0"
diff --git a/crates/ra_cargo_watch/src/lib.rs b/crates/ra_cargo_watch/src/lib.rs
index e7b700c10..ea7ddc86b 100644
--- a/crates/ra_cargo_watch/src/lib.rs
+++ b/crates/ra_cargo_watch/src/lib.rs
@@ -9,7 +9,7 @@ use lsp_types::{
 };
 use std::{
     collections::HashMap,
-    io::BufReader,
+    io::{BufRead, BufReader},
     path::PathBuf,
     process::{Command, Stdio},
     sync::Arc,
@@ -216,8 +216,10 @@ impl CheckWatcherThread {
                 self.last_update_req.take();
                 task_send.send(CheckTask::ClearDiagnostics).unwrap();
 
-                // By replacing the watcher, we drop the previous one which
-                // causes it to shut down automatically.
+                // Replace with a dummy watcher first so we drop the original and wait for completion
+                std::mem::replace(&mut self.watcher, WatchThread::dummy());
+
+                // Then create the actual new watcher
                 self.watcher = WatchThread::new(&self.options, &self.workspace_root);
             }
         }
@@ -348,17 +350,45 @@ impl WatchThread {
             // which will break out of the loop, and continue the shutdown
             let _ = message_send.send(CheckEvent::Begin);
 
-            for message in
-                cargo_metadata::parse_messages(BufReader::new(command.stdout.take().unwrap()))
-            {
+            // We manually read a line at a time, instead of using serde's
+            // stream deserializers, because the deserializer cannot recover
+            // from an error, resulting in it getting stuck, because we try to
+            // be resillient against failures.
+            //
+            // Because cargo only outputs one JSON object per line, we can
+            // simply skip a line if it doesn't parse, which just ignores any
+            // erroneus output.
+            let stdout = BufReader::new(command.stdout.take().unwrap());
+            for line in stdout.lines() {
+                let line = match line {
+                    Ok(line) => line,
+                    Err(err) => {
+                        log::error!("Couldn't read line from cargo: {}", err);
+                        continue;
+                    }
+                };
+
+                let message = serde_json::from_str::<cargo_metadata::Message>(&line);
                 let message = match message {
                     Ok(message) => message,
                     Err(err) => {
-                        log::error!("Invalid json from cargo check, ignoring: {}", err);
+                        log::error!(
+                            "Invalid json from cargo check, ignoring ({}): {:?} ",
+                            err,
+                            line
+                        );
                         continue;
                     }
                 };
 
+                // Skip certain kinds of messages to only spend time on what's useful
+                match &message {
+                    Message::CompilerArtifact(artifact) if artifact.fresh => continue,
+                    Message::BuildScriptExecuted(_) => continue,
+                    Message::Unknown => continue,
+                    _ => {}
+                }
+
                 match message_send.send(CheckEvent::Msg(message)) {
                     Ok(()) => {}
                     Err(_err) => {
diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index e6079b88d..a77bf6de6 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -1,20 +1,24 @@
 //! FIXME: write short doc here
 
 pub use hir_def::db::{
-    BodyQuery, BodyWithSourceMapQuery, ComputeCrateDefMapQuery, ConstDataQuery,
+    AttrsQuery, BodyQuery, BodyWithSourceMapQuery, ComputeCrateDefMapQuery, ConstDataQuery,
     CrateLangItemsQuery, DefDatabase, DefDatabaseStorage, DocumentationQuery, EnumDataQuery,
-    ExprScopesQuery, FunctionDataQuery, GenericParamsQuery, ImplDataQuery, InternDatabase,
-    InternDatabaseStorage, LangItemQuery, ModuleLangItemsQuery, RawItemsQuery, StaticDataQuery,
-    StructDataQuery, TraitDataQuery, TypeAliasDataQuery,
+    ExprScopesQuery, FunctionDataQuery, GenericParamsQuery, ImplDataQuery, InternConstQuery,
+    InternDatabase, InternDatabaseStorage, InternEnumQuery, InternFunctionQuery, InternImplQuery,
+    InternStaticQuery, InternStructQuery, InternTraitQuery, InternTypeAliasQuery, InternUnionQuery,
+    LangItemQuery, ModuleLangItemsQuery, RawItemsQuery, StaticDataQuery, StructDataQuery,
+    TraitDataQuery, TypeAliasDataQuery, UnionDataQuery,
 };
 pub use hir_expand::db::{
-    AstDatabase, AstDatabaseStorage, AstIdMapQuery, MacroArgQuery, MacroDefQuery, MacroExpandQuery,
-    ParseMacroQuery,
+    AstDatabase, AstDatabaseStorage, AstIdMapQuery, InternMacroQuery, MacroArgQuery, MacroDefQuery,
+    MacroExpandQuery, ParseMacroQuery,
 };
 pub use hir_ty::db::{
-    AssociatedTyDataQuery, CallableItemSignatureQuery, DoInferQuery, FieldTypesQuery,
-    GenericDefaultsQuery, GenericPredicatesQuery, HirDatabase, HirDatabaseStorage, ImplDatumQuery,
-    ImplsForTraitQuery, ImplsInCrateQuery, StructDatumQuery, TraitDatumQuery, TraitSolveQuery,
+    AssociatedTyDataQuery, AssociatedTyValueQuery, CallableItemSignatureQuery, DoInferQuery,
+    FieldTypesQuery, GenericDefaultsQuery, GenericPredicatesForParamQuery, GenericPredicatesQuery,
+    HirDatabase, HirDatabaseStorage, ImplDatumQuery, ImplSelfTyQuery, ImplTraitQuery,
+    ImplsForTraitQuery, ImplsInCrateQuery, InternAssocTyValueQuery, InternChalkImplQuery,
+    InternTypeCtorQuery, StructDatumQuery, TraitDatumQuery, TraitSolveQuery, TraitSolverQuery,
     TyQuery, ValueTyQuery,
 };
 
diff --git a/crates/ra_hir_def/src/find_path.rs b/crates/ra_hir_def/src/find_path.rs
index 8cc2fb160..43b9b124a 100644
--- a/crates/ra_hir_def/src/find_path.rs
+++ b/crates/ra_hir_def/src/find_path.rs
@@ -7,10 +7,39 @@ use crate::{
     visibility::Visibility,
     CrateId, ModuleDefId, ModuleId,
 };
-use hir_expand::name::Name;
+use hir_expand::name::{known, Name};
+use test_utils::tested_by;
 
 const MAX_PATH_LEN: usize = 15;
 
+impl ModPath {
+    fn starts_with_std(&self) -> bool {
+        self.segments.first().filter(|&first_segment| first_segment == &known::std).is_some()
+    }
+
+    // When std library is present, paths starting with `std::`
+    // should be preferred over paths starting with `core::` and `alloc::`
+    fn should_start_with_std(&self) -> bool {
+        self.segments
+            .first()
+            .filter(|&first_segment| {
+                first_segment == &known::alloc || first_segment == &known::core
+            })
+            .is_some()
+    }
+
+    fn len(&self) -> usize {
+        self.segments.len()
+            + match self.kind {
+                PathKind::Plain => 0,
+                PathKind::Super(i) => i as usize,
+                PathKind::Crate => 1,
+                PathKind::Abs => 0,
+                PathKind::DollarCrate(_) => 1,
+            }
+    }
+}
+
 // FIXME: handle local items
 
 /// Find a path that can be used to refer to a certain item. This can depend on
@@ -112,23 +141,27 @@ fn find_path_inner(
             Some(path) => path,
         };
         path.segments.push(name);
-        if path_len(&path) < best_path_len {
-            best_path_len = path_len(&path);
-            best_path = Some(path);
-        }
+
+        let new_path =
+            if let Some(best_path) = best_path { select_best_path(best_path, path) } else { path };
+        best_path_len = new_path.len();
+        best_path = Some(new_path);
     }
     best_path
 }
 
-fn path_len(path: &ModPath) -> usize {
-    path.segments.len()
-        + match path.kind {
-            PathKind::Plain => 0,
-            PathKind::Super(i) => i as usize,
-            PathKind::Crate => 1,
-            PathKind::Abs => 0,
-            PathKind::DollarCrate(_) => 1,
-        }
+fn select_best_path(old_path: ModPath, new_path: ModPath) -> ModPath {
+    if old_path.starts_with_std() && new_path.should_start_with_std() {
+        tested_by!(prefer_std_paths);
+        old_path
+    } else if new_path.starts_with_std() && old_path.should_start_with_std() {
+        tested_by!(prefer_std_paths);
+        new_path
+    } else if new_path.len() < old_path.len() {
+        new_path
+    } else {
+        old_path
+    }
 }
 
 fn find_importable_locations(
@@ -201,6 +234,7 @@ mod tests {
     use hir_expand::hygiene::Hygiene;
     use ra_db::fixture::WithFixture;
     use ra_syntax::ast::AstNode;
+    use test_utils::covers;
 
     /// `code` needs to contain a cursor marker; checks that `find_path` for the
     /// item the `path` refers to returns that same path when called from the
@@ -452,4 +486,41 @@ mod tests {
         "#;
         check_found_path(code, "crate::foo::S");
     }
+
+    #[test]
+    fn prefer_std_paths_over_alloc() {
+        covers!(prefer_std_paths);
+        let code = r#"
+        //- /main.rs crate:main deps:alloc,std
+        <|>
+
+        //- /std.rs crate:std deps:alloc
+        pub mod sync {
+            pub use alloc::sync::Arc;
+        }
+
+        //- /zzz.rs crate:alloc
+        pub mod sync {
+            pub struct Arc;
+        }
+        "#;
+        check_found_path(code, "std::sync::Arc");
+    }
+
+    #[test]
+    fn prefer_shorter_paths_if_not_alloc() {
+        let code = r#"
+        //- /main.rs crate:main deps:megaalloc,std
+        <|>
+
+        //- /std.rs crate:std deps:megaalloc
+        pub mod sync {
+            pub use megaalloc::sync::Arc;
+        }
+
+        //- /zzz.rs crate:megaalloc
+        pub struct Arc;
+        "#;
+        check_found_path(code, "megaalloc::Arc");
+    }
 }
diff --git a/crates/ra_hir_def/src/marks.rs b/crates/ra_hir_def/src/marks.rs
index 457ba4abe..daa49d5f1 100644
--- a/crates/ra_hir_def/src/marks.rs
+++ b/crates/ra_hir_def/src/marks.rs
@@ -13,4 +13,5 @@ test_utils::marks!(
     macro_dollar_crate_self
     macro_dollar_crate_other
     infer_resolve_while_let
+    prefer_std_paths
 );
diff --git a/crates/ra_hir_def/src/nameres.rs b/crates/ra_hir_def/src/nameres.rs
index 27c12e46c..852304dd0 100644
--- a/crates/ra_hir_def/src/nameres.rs
+++ b/crates/ra_hir_def/src/nameres.rs
@@ -229,6 +229,46 @@ impl CrateDefMap {
             self.resolve_path_fp_with_macro(db, ResolveMode::Other, original_module, path, shadow);
         (res.resolved_def, res.segment_index)
     }
+
+    // FIXME: this can use some more human-readable format (ideally, an IR
+    // even), as this should be a great debugging aid.
+    pub fn dump(&self) -> String {
+        let mut buf = String::new();
+        go(&mut buf, self, "\ncrate", self.root);
+        return buf.trim().to_string();
+
+        fn go(buf: &mut String, map: &CrateDefMap, path: &str, module: LocalModuleId) {
+            *buf += path;
+            *buf += "\n";
+
+            let mut entries: Vec<_> = map.modules[module].scope.resolutions().collect();
+            entries.sort_by_key(|(name, _)| name.clone());
+
+            for (name, def) in entries {
+                *buf += &format!("{}:", name);
+
+                if def.types.is_some() {
+                    *buf += " t";
+                }
+                if def.values.is_some() {
+                    *buf += " v";
+                }
+                if def.macros.is_some() {
+                    *buf += " m";
+                }
+                if def.is_none() {
+                    *buf += " _";
+                }
+
+                *buf += "\n";
+            }
+
+            for (name, child) in map.modules[module].children.iter() {
+                let path = path.to_string() + &format!("::{}", name);
+                go(buf, map, &path, *child);
+            }
+        }
+    }
 }
 
 impl ModuleData {
diff --git a/crates/ra_hir_def/src/nameres/tests.rs b/crates/ra_hir_def/src/nameres/tests.rs
index 78bcdc850..82f0f835c 100644
--- a/crates/ra_hir_def/src/nameres/tests.rs
+++ b/crates/ra_hir_def/src/nameres/tests.rs
@@ -10,11 +10,10 @@ use insta::assert_snapshot;
 use ra_db::{fixture::WithFixture, SourceDatabase};
 use test_utils::covers;
 
-use crate::{db::DefDatabase, nameres::*, test_db::TestDB, LocalModuleId};
+use crate::{db::DefDatabase, nameres::*, test_db::TestDB};
 
 fn def_map(fixture: &str) -> String {
-    let dm = compute_crate_def_map(fixture);
-    render_crate_def_map(&dm)
+    compute_crate_def_map(fixture).dump()
 }
 
 fn compute_crate_def_map(fixture: &str) -> Arc<CrateDefMap> {
@@ -23,44 +22,6 @@ fn compute_crate_def_map(fixture: &str) -> Arc<CrateDefMap> {
     db.crate_def_map(krate)
 }
 
-fn render_crate_def_map(map: &CrateDefMap) -> String {
-    let mut buf = String::new();
-    go(&mut buf, map, "\ncrate", map.root);
-    return buf.trim().to_string();
-
-    fn go(buf: &mut String, map: &CrateDefMap, path: &str, module: LocalModuleId) {
-        *buf += path;
-        *buf += "\n";
-
-        let mut entries: Vec<_> = map.modules[module].scope.resolutions().collect();
-        entries.sort_by_key(|(name, _)| name.clone());
-
-        for (name, def) in entries {
-            *buf += &format!("{}:", name);
-
-            if def.types.is_some() {
-                *buf += " t";
-            }
-            if def.values.is_some() {
-                *buf += " v";
-            }
-            if def.macros.is_some() {
-                *buf += " m";
-            }
-            if def.is_none() {
-                *buf += " _";
-            }
-
-            *buf += "\n";
-        }
-
-        for (name, child) in map.modules[module].children.iter() {
-            let path = path.to_string() + &format!("::{}", name);
-            go(buf, map, &path, *child);
-        }
-    }
-}
-
 #[test]
 fn crate_def_map_smoke_test() {
     let map = def_map(
diff --git a/crates/ra_hir_expand/src/name.rs b/crates/ra_hir_expand/src/name.rs
index b3fa1efba..b2e10f445 100644
--- a/crates/ra_hir_expand/src/name.rs
+++ b/crates/ra_hir_expand/src/name.rs
@@ -141,6 +141,8 @@ pub mod known {
         macro_rules,
         // Components of known path (value or mod name)
         std,
+        core,
+        alloc,
         iter,
         ops,
         future,
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index 908e4862d..08d501ccd 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -847,7 +847,7 @@ impl HirDisplay for ApplicationTy {
             }
             TypeCtor::Array => {
                 let t = self.parameters.as_single();
-                write!(f, "[{};_]", t.display(f.db))?;
+                write!(f, "[{}; _]", t.display(f.db))?;
             }
             TypeCtor::RawPtr(m) => {
                 let t = self.parameters.as_single();
diff --git a/crates/ra_hir_ty/src/tests/coercion.rs b/crates/ra_hir_ty/src/tests/coercion.rs
index 7e99a42ed..76a1b46c0 100644
--- a/crates/ra_hir_ty/src/tests/coercion.rs
+++ b/crates/ra_hir_ty/src/tests/coercion.rs
@@ -71,42 +71,42 @@ fn test2() {
     [82; 93) '{ loop {} }': T
     [84; 91) 'loop {}': !
     [89; 91) '{}': ()
-    [122; 133) '{ loop {} }': *mut [T;_]
+    [122; 133) '{ loop {} }': *mut [T; _]
     [124; 131) 'loop {}': !
     [129; 131) '{}': ()
     [160; 173) '{     gen() }': *mut [U]
-    [166; 169) 'gen': fn gen<U>() -> *mut [T;_]
-    [166; 171) 'gen()': *mut [U;_]
+    [166; 169) 'gen': fn gen<U>() -> *mut [T; _]
+    [166; 171) 'gen()': *mut [U; _]
     [186; 420) '{     ...rr); }': ()
-    [196; 199) 'arr': &[u8;_]
-    [212; 216) '&[1]': &[u8;_]
-    [213; 216) '[1]': [u8;_]
+    [196; 199) 'arr': &[u8; _]
+    [212; 216) '&[1]': &[u8; _]
+    [213; 216) '[1]': [u8; _]
     [214; 215) '1': u8
     [227; 228) 'a': &[u8]
-    [237; 240) 'arr': &[u8;_]
+    [237; 240) 'arr': &[u8; _]
     [250; 251) 'b': u8
     [254; 255) 'f': fn f<u8>(&[T]) -> T
     [254; 260) 'f(arr)': u8
-    [256; 259) 'arr': &[u8;_]
+    [256; 259) 'arr': &[u8; _]
     [270; 271) 'c': &[u8]
     [280; 287) '{ arr }': &[u8]
-    [282; 285) 'arr': &[u8;_]
+    [282; 285) 'arr': &[u8; _]
     [297; 298) 'd': u8
     [301; 302) 'g': fn g<u8>(S<&[T]>) -> T
     [301; 316) 'g(S { a: arr })': u8
     [303; 315) 'S { a: arr }': S<&[u8]>
-    [310; 313) 'arr': &[u8;_]
-    [326; 327) 'e': [&[u8];_]
-    [341; 346) '[arr]': [&[u8];_]
-    [342; 345) 'arr': &[u8;_]
-    [356; 357) 'f': [&[u8];_]
-    [371; 379) '[arr; 2]': [&[u8];_]
-    [372; 375) 'arr': &[u8;_]
+    [310; 313) 'arr': &[u8; _]
+    [326; 327) 'e': [&[u8]; _]
+    [341; 346) '[arr]': [&[u8]; _]
+    [342; 345) 'arr': &[u8; _]
+    [356; 357) 'f': [&[u8]; _]
+    [371; 379) '[arr; 2]': [&[u8]; _]
+    [372; 375) 'arr': &[u8; _]
     [377; 378) '2': usize
     [389; 390) 'g': (&[u8], &[u8])
     [407; 417) '(arr, arr)': (&[u8], &[u8])
-    [408; 411) 'arr': &[u8;_]
-    [413; 416) 'arr': &[u8;_]
+    [408; 411) 'arr': &[u8; _]
+    [413; 416) 'arr': &[u8; _]
     "###
     );
 }
@@ -122,8 +122,8 @@ fn test() {
         @r###"
     [11; 40) '{     ...[1]; }': ()
     [21; 22) 'x': &[i32]
-    [33; 37) '&[1]': &[i32;_]
-    [34; 37) '[1]': [i32;_]
+    [33; 37) '&[1]': &[i32; _]
+    [34; 37) '[1]': [i32; _]
     [35; 36) '1': i32
     "###);
 }
@@ -159,22 +159,22 @@ fn test(a: A<[u8; 2]>, b: B<[u8; 2]>, c: C<[u8; 2]>) {
     [334; 335) 'x': C<[T]>
     [355; 360) '{ x }': C<[T]>
     [357; 358) 'x': C<[T]>
-    [370; 371) 'a': A<[u8;_]>
-    [385; 386) 'b': B<[u8;_]>
-    [400; 401) 'c': C<[u8;_]>
+    [370; 371) 'a': A<[u8; _]>
+    [385; 386) 'b': B<[u8; _]>
+    [400; 401) 'c': C<[u8; _]>
     [415; 481) '{     ...(c); }': ()
     [425; 426) 'd': A<[{unknown}]>
     [429; 433) 'foo1': fn foo1<{unknown}>(A<[T]>) -> A<[T]>
     [429; 436) 'foo1(a)': A<[{unknown}]>
-    [434; 435) 'a': A<[u8;_]>
+    [434; 435) 'a': A<[u8; _]>
     [446; 447) 'e': B<[u8]>
     [450; 454) 'foo2': fn foo2<u8>(B<[T]>) -> B<[T]>
     [450; 457) 'foo2(b)': B<[u8]>
-    [455; 456) 'b': B<[u8;_]>
+    [455; 456) 'b': B<[u8; _]>
     [467; 468) 'f': C<[u8]>
     [471; 475) 'foo3': fn foo3<u8>(C<[T]>) -> C<[T]>
     [471; 478) 'foo3(c)': C<[u8]>
-    [476; 477) 'c': C<[u8;_]>
+    [476; 477) 'c': C<[u8; _]>
     "###
     );
 }
@@ -204,12 +204,12 @@ fn test() {
     [72; 97) '{     ...     }': &[i32]
     [82; 85) 'foo': fn foo<i32>(&[T]) -> &[T]
     [82; 91) 'foo(&[1])': &[i32]
-    [86; 90) '&[1]': &[i32;_]
-    [87; 90) '[1]': [i32;_]
+    [86; 90) '&[1]': &[i32; _]
+    [87; 90) '[1]': [i32; _]
     [88; 89) '1': i32
-    [103; 123) '{     ...     }': &[i32;_]
-    [113; 117) '&[1]': &[i32;_]
-    [114; 117) '[1]': [i32;_]
+    [103; 123) '{     ...     }': &[i32; _]
+    [113; 117) '&[1]': &[i32; _]
+    [114; 117) '[1]': [i32; _]
     [115; 116) '1': i32
     "###
     );
@@ -237,15 +237,15 @@ fn test() {
     [60; 61) 'x': &[i32]
     [64; 123) 'if tru...     }': &[i32]
     [67; 71) 'true': bool
-    [72; 92) '{     ...     }': &[i32;_]
-    [82; 86) '&[1]': &[i32;_]
-    [83; 86) '[1]': [i32;_]
+    [72; 92) '{     ...     }': &[i32; _]
+    [82; 86) '&[1]': &[i32; _]
+    [83; 86) '[1]': [i32; _]
     [84; 85) '1': i32
     [98; 123) '{     ...     }': &[i32]
     [108; 111) 'foo': fn foo<i32>(&[T]) -> &[T]
     [108; 117) 'foo(&[1])': &[i32]
-    [112; 116) '&[1]': &[i32;_]
-    [113; 116) '[1]': [i32;_]
+    [112; 116) '&[1]': &[i32; _]
+    [113; 116) '[1]': [i32; _]
     [114; 115) '1': i32
     "###
     );
@@ -277,16 +277,16 @@ fn test(i: i32) {
     [88; 89) '2': i32
     [93; 96) 'foo': fn foo<i32>(&[T]) -> &[T]
     [93; 102) 'foo(&[2])': &[i32]
-    [97; 101) '&[2]': &[i32;_]
-    [98; 101) '[2]': [i32;_]
+    [97; 101) '&[2]': &[i32; _]
+    [98; 101) '[2]': [i32; _]
     [99; 100) '2': i32
     [112; 113) '1': i32
-    [117; 121) '&[1]': &[i32;_]
-    [118; 121) '[1]': [i32;_]
+    [117; 121) '&[1]': &[i32; _]
+    [118; 121) '[1]': [i32; _]
     [119; 120) '1': i32
     [131; 132) '_': i32
-    [136; 140) '&[3]': &[i32;_]
-    [137; 140) '[3]': [i32;_]
+    [136; 140) '&[3]': &[i32; _]
+    [137; 140) '[3]': [i32; _]
     [138; 139) '3': i32
     "###
     );
@@ -316,18 +316,18 @@ fn test(i: i32) {
     [70; 147) 'match ...     }': &[i32]
     [76; 77) 'i': i32
     [88; 89) '1': i32
-    [93; 97) '&[1]': &[i32;_]
-    [94; 97) '[1]': [i32;_]
+    [93; 97) '&[1]': &[i32; _]
+    [94; 97) '[1]': [i32; _]
     [95; 96) '1': i32
     [107; 108) '2': i32
     [112; 115) 'foo': fn foo<i32>(&[T]) -> &[T]
     [112; 121) 'foo(&[2])': &[i32]
-    [116; 120) '&[2]': &[i32;_]
-    [117; 120) '[2]': [i32;_]
+    [116; 120) '&[2]': &[i32; _]
+    [117; 120) '[2]': [i32; _]
     [118; 119) '2': i32
     [131; 132) '_': i32
-    [136; 140) '&[3]': &[i32;_]
-    [137; 140) '[3]': [i32;_]
+    [136; 140) '&[3]': &[i32; _]
+    [137; 140) '[3]': [i32; _]
     [138; 139) '3': i32
     "###
     );
diff --git a/crates/ra_hir_ty/src/tests/regression.rs b/crates/ra_hir_ty/src/tests/regression.rs
index aa948dcbf..02bab6dbe 100644
--- a/crates/ra_hir_ty/src/tests/regression.rs
+++ b/crates/ra_hir_ty/src/tests/regression.rs
@@ -102,7 +102,7 @@ fn test() {
     [11; 48) '{     ...&y]; }': ()
     [21; 22) 'y': &{unknown}
     [25; 32) 'unknown': &{unknown}
-    [38; 45) '[y, &y]': [&&{unknown};_]
+    [38; 45) '[y, &y]': [&&{unknown}; _]
     [39; 40) 'y': &{unknown}
     [42; 44) '&y': &&{unknown}
     [43; 44) 'y': &{unknown}
@@ -128,7 +128,7 @@ fn test() {
     [25; 32) 'unknown': &&{unknown}
     [42; 43) 'y': &&{unknown}
     [46; 53) 'unknown': &&{unknown}
-    [59; 77) '[(x, y..., &x)]': [(&&&{unknown}, &&&{unknown});_]
+    [59; 77) '[(x, y..., &x)]': [(&&&{unknown}, &&&{unknown}); _]
     [60; 66) '(x, y)': (&&&{unknown}, &&&{unknown})
     [61; 62) 'x': &&{unknown}
     [64; 65) 'y': &&{unknown}
@@ -180,8 +180,8 @@ fn test_line_buffer() {
 "#),
         @r###"
     [23; 53) '{     ...n']; }': ()
-    [29; 50) '&[0, b...b'\n']': &[u8;_]
-    [30; 50) '[0, b'...b'\n']': [u8;_]
+    [29; 50) '&[0, b...b'\n']': &[u8; _]
+    [30; 50) '[0, b'...b'\n']': [u8; _]
     [31; 32) '0': u8
     [34; 39) 'b'\n'': u8
     [41; 42) '1': u8
diff --git a/crates/ra_hir_ty/src/tests/simple.rs b/crates/ra_hir_ty/src/tests/simple.rs
index b7204ec00..fdab9c187 100644
--- a/crates/ra_hir_ty/src/tests/simple.rs
+++ b/crates/ra_hir_ty/src/tests/simple.rs
@@ -28,7 +28,7 @@ mod boxed {
 
 "#,
     );
-    assert_eq!("(Box<i32>, Box<Box<i32>>, Box<&i32>, Box<[i32;_]>)", type_at_pos(&db, pos));
+    assert_eq!("(Box<i32>, Box<Box<i32>>, Box<&i32>, Box<[i32; _]>)", type_at_pos(&db, pos));
 }
 
 #[test]
@@ -1061,55 +1061,55 @@ fn test(x: &str, y: isize) {
     [9; 10) 'x': &str
     [18; 19) 'y': isize
     [28; 293) '{     ... []; }': ()
-    [38; 39) 'a': [&str;_]
-    [42; 45) '[x]': [&str;_]
+    [38; 39) 'a': [&str; _]
+    [42; 45) '[x]': [&str; _]
     [43; 44) 'x': &str
-    [55; 56) 'b': [[&str;_];_]
-    [59; 65) '[a, a]': [[&str;_];_]
-    [60; 61) 'a': [&str;_]
-    [63; 64) 'a': [&str;_]
-    [75; 76) 'c': [[[&str;_];_];_]
-    [79; 85) '[b, b]': [[[&str;_];_];_]
-    [80; 81) 'b': [[&str;_];_]
-    [83; 84) 'b': [[&str;_];_]
-    [96; 97) 'd': [isize;_]
-    [100; 112) '[y, 1, 2, 3]': [isize;_]
+    [55; 56) 'b': [[&str; _]; _]
+    [59; 65) '[a, a]': [[&str; _]; _]
+    [60; 61) 'a': [&str; _]
+    [63; 64) 'a': [&str; _]
+    [75; 76) 'c': [[[&str; _]; _]; _]
+    [79; 85) '[b, b]': [[[&str; _]; _]; _]
+    [80; 81) 'b': [[&str; _]; _]
+    [83; 84) 'b': [[&str; _]; _]
+    [96; 97) 'd': [isize; _]
+    [100; 112) '[y, 1, 2, 3]': [isize; _]
     [101; 102) 'y': isize
     [104; 105) '1': isize
     [107; 108) '2': isize
     [110; 111) '3': isize
-    [122; 123) 'd': [isize;_]
-    [126; 138) '[1, y, 2, 3]': [isize;_]
+    [122; 123) 'd': [isize; _]
+    [126; 138) '[1, y, 2, 3]': [isize; _]
     [127; 128) '1': isize
     [130; 131) 'y': isize
     [133; 134) '2': isize
     [136; 137) '3': isize
-    [148; 149) 'e': [isize;_]
-    [152; 155) '[y]': [isize;_]
+    [148; 149) 'e': [isize; _]
+    [152; 155) '[y]': [isize; _]
     [153; 154) 'y': isize
-    [165; 166) 'f': [[isize;_];_]
-    [169; 175) '[d, d]': [[isize;_];_]
-    [170; 171) 'd': [isize;_]
-    [173; 174) 'd': [isize;_]
-    [185; 186) 'g': [[isize;_];_]
-    [189; 195) '[e, e]': [[isize;_];_]
-    [190; 191) 'e': [isize;_]
-    [193; 194) 'e': [isize;_]
-    [206; 207) 'h': [i32;_]
-    [210; 216) '[1, 2]': [i32;_]
+    [165; 166) 'f': [[isize; _]; _]
+    [169; 175) '[d, d]': [[isize; _]; _]
+    [170; 171) 'd': [isize; _]
+    [173; 174) 'd': [isize; _]
+    [185; 186) 'g': [[isize; _]; _]
+    [189; 195) '[e, e]': [[isize; _]; _]
+    [190; 191) 'e': [isize; _]
+    [193; 194) 'e': [isize; _]
+    [206; 207) 'h': [i32; _]
+    [210; 216) '[1, 2]': [i32; _]
     [211; 212) '1': i32
     [214; 215) '2': i32
-    [226; 227) 'i': [&str;_]
-    [230; 240) '["a", "b"]': [&str;_]
+    [226; 227) 'i': [&str; _]
+    [230; 240) '["a", "b"]': [&str; _]
     [231; 234) '"a"': &str
     [236; 239) '"b"': &str
-    [251; 252) 'b': [[&str;_];_]
-    [255; 265) '[a, ["b"]]': [[&str;_];_]
-    [256; 257) 'a': [&str;_]
-    [259; 264) '["b"]': [&str;_]
+    [251; 252) 'b': [[&str; _]; _]
+    [255; 265) '[a, ["b"]]': [[&str; _]; _]
+    [256; 257) 'a': [&str; _]
+    [259; 264) '["b"]': [&str; _]
     [260; 263) '"b"': &str
-    [275; 276) 'x': [u8;_]
-    [288; 290) '[]': [u8;_]
+    [275; 276) 'x': [u8; _]
+    [288; 290) '[]': [u8; _]
     "###
     );
 }
diff --git a/crates/ra_hir_ty/src/tests/traits.rs b/crates/ra_hir_ty/src/tests/traits.rs
index bc20a49cc..a6ac18f86 100644
--- a/crates/ra_hir_ty/src/tests/traits.rs
+++ b/crates/ra_hir_ty/src/tests/traits.rs
@@ -479,7 +479,7 @@ fn indexing_arrays() {
         @r###"
     [10; 26) '{ &mut...[2]; }': ()
     [12; 23) '&mut [9][2]': &mut {unknown}
-    [17; 20) '[9]': [i32;_]
+    [17; 20) '[9]': [i32; _]
     [17; 23) '[9][2]': {unknown}
     [18; 19) '9': i32
     [21; 22) '2': i32
diff --git a/crates/ra_ide/src/change.rs b/crates/ra_ide/src/change.rs
index ce617840c..45a58690b 100644
--- a/crates/ra_ide/src/change.rs
+++ b/crates/ra_ide/src/change.rs
@@ -301,45 +301,74 @@ impl RootDatabase {
             )*}
         }
         sweep_each_query![
+            // SourceDatabase
             ra_db::ParseQuery
             ra_db::SourceRootCratesQuery
+
+            // AstDatabase
             hir::db::AstIdMapQuery
-            hir::db::ParseMacroQuery
-            hir::db::MacroDefQuery
+            hir::db::InternMacroQuery
             hir::db::MacroArgQuery
+            hir::db::MacroDefQuery
+            hir::db::ParseMacroQuery
             hir::db::MacroExpandQuery
+
+            // DefDatabase
+            hir::db::RawItemsQuery
+            hir::db::ComputeCrateDefMapQuery
             hir::db::StructDataQuery
+            hir::db::UnionDataQuery
             hir::db::EnumDataQuery
+            hir::db::ImplDataQuery
             hir::db::TraitDataQuery
-            hir::db::RawItemsQuery
-            hir::db::ComputeCrateDefMapQuery
-            hir::db::GenericParamsQuery
-            hir::db::FunctionDataQuery
             hir::db::TypeAliasDataQuery
+            hir::db::FunctionDataQuery
             hir::db::ConstDataQuery
             hir::db::StaticDataQuery
+            hir::db::BodyWithSourceMapQuery
+            hir::db::BodyQuery
+            hir::db::ExprScopesQuery
+            hir::db::GenericParamsQuery
+            hir::db::AttrsQuery
             hir::db::ModuleLangItemsQuery
             hir::db::CrateLangItemsQuery
             hir::db::LangItemQuery
             hir::db::DocumentationQuery
-            hir::db::ExprScopesQuery
+
+            // InternDatabase
+            hir::db::InternFunctionQuery
+            hir::db::InternStructQuery
+            hir::db::InternUnionQuery
+            hir::db::InternEnumQuery
+            hir::db::InternConstQuery
+            hir::db::InternStaticQuery
+            hir::db::InternTraitQuery
+            hir::db::InternTypeAliasQuery
+            hir::db::InternImplQuery
+
+            // HirDatabase
             hir::db::DoInferQuery
             hir::db::TyQuery
             hir::db::ValueTyQuery
+            hir::db::ImplSelfTyQuery
+            hir::db::ImplTraitQuery
             hir::db::FieldTypesQuery
             hir::db::CallableItemSignatureQuery
+            hir::db::GenericPredicatesForParamQuery
             hir::db::GenericPredicatesQuery
             hir::db::GenericDefaultsQuery
-            hir::db::BodyWithSourceMapQuery
-            hir::db::BodyQuery
             hir::db::ImplsInCrateQuery
             hir::db::ImplsForTraitQuery
+            hir::db::TraitSolverQuery
+            hir::db::InternTypeCtorQuery
+            hir::db::InternChalkImplQuery
+            hir::db::InternAssocTyValueQuery
             hir::db::AssociatedTyDataQuery
+            hir::db::AssociatedTyValueQuery
+            hir::db::TraitSolveQuery
             hir::db::TraitDatumQuery
             hir::db::StructDatumQuery
             hir::db::ImplDatumQuery
-            hir::db::ImplDataQuery
-            hir::db::TraitSolveQuery
         ];
         acc.sort_by_key(|it| std::cmp::Reverse(it.1));
         acc
diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 15bf519c9..d850ded37 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -5,11 +5,18 @@ mod handlers;
 mod subscriptions;
 pub(crate) mod pending_requests;
 
-use std::{error::Error, fmt, panic, path::PathBuf, sync::Arc, time::Instant};
+use std::{
+    env,
+    error::Error,
+    fmt, panic,
+    path::PathBuf,
+    sync::Arc,
+    time::{Duration, Instant},
+};
 
 use crossbeam_channel::{select, unbounded, RecvError, Sender};
 use lsp_server::{Connection, ErrorCode, Message, Notification, Request, RequestId, Response};
-use lsp_types::{ClientCapabilities, NumberOrString, Url};
+use lsp_types::{ClientCapabilities, NumberOrString};
 use ra_cargo_watch::{CheckOptions, CheckTask};
 use ra_ide::{Canceled, FeatureFlags, FileId, LibraryData, SourceRootId};
 use ra_prof::profile;
@@ -352,7 +359,7 @@ fn loop_turn(
             world_state.maybe_collect_garbage();
             loop_state.in_flight_libraries -= 1;
         }
-        Event::CheckWatcher(task) => on_check_task(task, world_state, task_sender)?,
+        Event::CheckWatcher(task) => on_check_task(pool, task, world_state, task_sender)?,
         Event::Msg(msg) => match msg {
             Message::Request(req) => on_request(
                 world_state,
@@ -425,6 +432,19 @@ fn loop_turn(
             loop_state.subscriptions.subscriptions(),
         )
     }
+
+    let loop_duration = loop_start.elapsed();
+    if loop_duration > Duration::from_millis(100) {
+        log::error!("overly long loop turn: {:?}", loop_duration);
+        if env::var("RA_PROFILE").is_ok() {
+            show_message(
+                req::MessageType::Error,
+                format!("overly long loop turn: {:?}", loop_duration),
+                &connection.sender,
+            );
+        }
+    }
+
     Ok(())
 }
 
@@ -452,7 +472,7 @@ fn on_request(
     world: &mut WorldState,
     pending_requests: &mut PendingRequests,
     pool: &ThreadPool,
-    sender: &Sender<Task>,
+    task_sender: &Sender<Task>,
     msg_sender: &Sender<Message>,
     request_received: Instant,
     req: Request,
@@ -461,7 +481,7 @@ fn on_request(
         req: Some(req),
         pool,
         world,
-        sender,
+        task_sender,
         msg_sender,
         pending_requests,
         request_received,
@@ -602,31 +622,23 @@ fn on_notification(
 }
 
 fn on_check_task(
+    pool: &ThreadPool,
     task: CheckTask,
     world_state: &mut WorldState,
     task_sender: &Sender<Task>,
 ) -> Result<()> {
-    match task {
+    let urls = match task {
         CheckTask::ClearDiagnostics => {
             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 {
-                publish_diagnostics_for_url(&url, world_state, task_sender)?;
-            }
+            state.clear()
         }
 
         CheckTask::AddDiagnostic(url, 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
-            // receive updated diagnostics.
-            publish_diagnostics_for_url(&url, world_state, task_sender)?;
+            vec![url]
         }
 
         CheckTask::Status(progress) => {
@@ -636,22 +648,30 @@ fn on_check_task(
             };
             let not = notification_new::<req::Progress>(params);
             task_sender.send(Task::Notify(not)).unwrap();
+            Vec::new()
         }
-    }
-    Ok(())
-}
+    };
+
+    let subscriptions = urls
+        .into_iter()
+        .map(|url| {
+            let path = url.to_file_path().map_err(|()| format!("invalid uri: {}", url))?;
+            Ok(world_state.vfs.read().path2file(&path).map(|it| FileId(it.0)))
+        })
+        .filter_map(|res| res.transpose())
+        .collect::<Result<Vec<_>>>()?;
+
+    // We manually send a diagnostic update when the watcher asks
+    // us to, to avoid the issue of having to change the file to
+    // receive updated diagnostics.
+    update_file_notifications_on_threadpool(
+        pool,
+        world_state.snapshot(),
+        false,
+        task_sender.clone(),
+        subscriptions,
+    );
 
-fn publish_diagnostics_for_url(
-    url: &Url,
-    world_state: &WorldState,
-    task_sender: &Sender<Task>,
-) -> Result<()> {
-    let path = url.to_file_path().map_err(|()| format!("invalid uri: {}", url))?;
-    if let Some(file_id) = world_state.vfs.read().path2file(&path) {
-        let params = handlers::publish_diagnostics(&world_state.snapshot(), FileId(file_id.0))?;
-        let not = notification_new::<req::PublishDiagnostics>(params);
-        task_sender.send(Task::Notify(not)).unwrap();
-    }
     Ok(())
 }
 
@@ -661,7 +681,7 @@ struct PoolDispatcher<'a> {
     world: &'a mut WorldState,
     pending_requests: &'a mut PendingRequests,
     msg_sender: &'a Sender<Message>,
-    sender: &'a Sender<Task>,
+    task_sender: &'a Sender<Task>,
     request_received: Instant,
 }
 
@@ -708,7 +728,7 @@ impl<'a> PoolDispatcher<'a> {
 
         self.pool.execute({
             let world = self.world.snapshot();
-            let sender = self.sender.clone();
+            let sender = self.task_sender.clone();
             move || {
                 let result = f(world, params);
                 let task = result_to_task::<R>(id, result);
@@ -786,7 +806,7 @@ fn update_file_notifications_on_threadpool(
     pool: &ThreadPool,
     world: WorldSnapshot,
     publish_decorations: bool,
-    sender: Sender<Task>,
+    task_sender: Sender<Task>,
     subscriptions: Vec<FileId>,
 ) {
     log::trace!("updating notifications for {:?}", subscriptions);
@@ -802,7 +822,7 @@ fn update_file_notifications_on_threadpool(
                     }
                     Ok(params) => {
                         let not = notification_new::<req::PublishDiagnostics>(params);
-                        sender.send(Task::Notify(not)).unwrap();
+                        task_sender.send(Task::Notify(not)).unwrap();
                     }
                 }
             }
@@ -815,7 +835,7 @@ fn update_file_notifications_on_threadpool(
                     }
                     Ok(params) => {
                         let not = notification_new::<req::PublishDecorations>(params);
-                        sender.send(Task::Notify(not)).unwrap();
+                        task_sender.send(Task::Notify(not)).unwrap();
                     }
                 }
             }
diff --git a/crates/ra_prof/src/lib.rs b/crates/ra_prof/src/lib.rs
index c7973ddf4..4a49e9f95 100644
--- a/crates/ra_prof/src/lib.rs
+++ b/crates/ra_prof/src/lib.rs
@@ -6,9 +6,9 @@ mod google_cpu_profiler;
 
 use std::{
     cell::RefCell,
+    collections::BTreeMap,
     collections::HashSet,
     io::{stderr, Write},
-    iter::repeat,
     mem,
     sync::{
         atomic::{AtomicBool, Ordering},
@@ -17,7 +17,6 @@ use std::{
     time::{Duration, Instant},
 };
 
-use itertools::Itertools;
 use once_cell::sync::Lazy;
 
 pub use crate::memory_usage::{Bytes, MemoryUsage};
@@ -216,7 +215,7 @@ impl Drop for Profiler {
                         // (otherwise we could print `0ms` despite user's `>0` filter when
                         // `duration` is just a few nanos).
                         if duration.as_millis() > longer_than.as_millis() {
-                            print(0, &stack.messages, &mut stdout.lock(), longer_than, None);
+                            print(&stack.messages, longer_than, &mut stdout.lock());
                         }
                         stack.messages.clear();
                     }
@@ -227,59 +226,85 @@ impl Drop for Profiler {
     }
 }
 
-fn print(
-    lvl: usize,
-    msgs: &[Message],
-    out: &mut impl Write,
-    longer_than: Duration,
-    total: Option<Duration>,
-) {
+fn print(msgs: &[Message], longer_than: Duration, out: &mut impl Write) {
     if msgs.is_empty() {
         return;
     }
-    // The index of the first element that will be included in the slice when we recurse.
-    let mut next_start = 0;
-    let indent = repeat("    ").take(lvl).collect::<String>();
-    // We output hierarchy for long calls, but sum up all short calls
-    let mut short = Vec::new();
+    let children_map = idx_to_children(msgs);
+    let root_idx = msgs.len() - 1;
+    print_for_idx(root_idx, &children_map, msgs, longer_than, out);
+}
+
+fn print_for_idx(
+    current_idx: usize,
+    children_map: &[Vec<usize>],
+    msgs: &[Message],
+    longer_than: Duration,
+    out: &mut impl Write,
+) {
+    let current = &msgs[current_idx];
+    let current_indent = "    ".repeat(current.level);
+    writeln!(out, "{}{:5}ms - {}", current_indent, current.duration.as_millis(), current.message)
+        .expect("printing profiling info");
+
+    let longer_than_millis = longer_than.as_millis();
+    let children_indices = &children_map[current_idx];
     let mut accounted_for = Duration::default();
-    for (i, &Message { level, duration, message: ref msg }) in msgs.iter().enumerate() {
-        if level != lvl {
-            continue;
-        }
-        accounted_for += duration;
-        if duration.as_millis() > longer_than.as_millis() {
-            writeln!(out, "{}{:5}ms - {}", indent, duration.as_millis(), msg)
-                .expect("printing profiling info to stdout");
+    let mut short_children = BTreeMap::new(); // Use `BTreeMap` to get deterministic output.
 
-            print(lvl + 1, &msgs[next_start..i], out, longer_than, Some(duration));
+    for child_idx in children_indices.iter() {
+        let child = &msgs[*child_idx];
+        if child.duration.as_millis() > longer_than_millis {
+            print_for_idx(*child_idx, children_map, msgs, longer_than, out);
         } else {
-            short.push((msg, duration))
+            let pair = short_children.entry(&child.message).or_insert((Duration::default(), 0));
+            pair.0 += child.duration;
+            pair.1 += 1;
         }
+        accounted_for += child.duration;
+    }
 
-        next_start = i + 1;
+    for (child_msg, (duration, count)) in short_children.iter() {
+        let millis = duration.as_millis();
+        writeln!(out, "    {}{:5}ms - {} ({} calls)", current_indent, millis, child_msg, count)
+            .expect("printing profiling info");
     }
-    short.sort_by_key(|(msg, _time)| *msg);
-    for (msg, entires) in short.iter().group_by(|(msg, _time)| msg).into_iter() {
-        let mut count = 0;
-        let mut total_duration = Duration::default();
-        entires.for_each(|(_msg, time)| {
-            count += 1;
-            total_duration += *time;
-        });
-        writeln!(out, "{}{:5}ms - {} ({} calls)", indent, total_duration.as_millis(), msg, count)
-            .expect("printing profiling info to stdout");
+
+    let unaccounted_millis = (current.duration - accounted_for).as_millis();
+    if !children_indices.is_empty()
+        && unaccounted_millis > 0
+        && unaccounted_millis > longer_than_millis
+    {
+        writeln!(out, "    {}{:5}ms - ???", current_indent, unaccounted_millis)
+            .expect("printing profiling info");
     }
+}
 
-    if let Some(total) = total {
-        if let Some(unaccounted) = total.checked_sub(accounted_for) {
-            let unaccounted_millis = unaccounted.as_millis();
-            if unaccounted_millis > longer_than.as_millis() && unaccounted_millis > 0 {
-                writeln!(out, "{}{:5}ms - ???", indent, unaccounted_millis)
-                    .expect("printing profiling info to stdout");
-            }
+/// Returns a mapping from an index in the `msgs` to the vector with the indices of its children.
+///
+/// This assumes that the entries in `msgs` are in the order of when the calls to `profile` finish.
+/// In other words, a postorder of the call graph. In particular, the root is the last element of
+/// `msgs`.
+fn idx_to_children(msgs: &[Message]) -> Vec<Vec<usize>> {
+    // Initialize with the index of the root; `msgs` and `ancestors` should be never empty.
+    assert!(!msgs.is_empty());
+    let mut ancestors = vec![msgs.len() - 1];
+    let mut result: Vec<Vec<usize>> = vec![vec![]; msgs.len()];
+    for (idx, msg) in msgs[..msgs.len() - 1].iter().enumerate().rev() {
+        // We need to find the parent of the current message, i.e., the last ancestor that has a
+        // level lower than the current message.
+        while msgs[*ancestors.last().unwrap()].level >= msg.level {
+            ancestors.pop();
         }
+        result[*ancestors.last().unwrap()].push(idx);
+        ancestors.push(idx);
+    }
+    // Note that above we visited all children from the last to the first one. Let's reverse vectors
+    // to get the more natural order where the first element is the first child.
+    for vec in result.iter_mut() {
+        vec.reverse();
     }
+    result
 }
 
 /// Prints backtrace to stderr, useful for debugging.
@@ -388,7 +413,7 @@ mod tests {
             Message { level: 1, duration: Duration::from_nanos(2), message: "bar".to_owned() },
             Message { level: 0, duration: Duration::from_millis(1), message: "foo".to_owned() },
         ];
-        print(0, &msgs, &mut result, Duration::from_millis(0), Some(Duration::from_millis(1)));
+        print(&msgs, Duration::from_millis(0), &mut result);
         // The calls to `bar` are so short that they'll be rounded to 0ms and should get collapsed
         // when printing.
         assert_eq!(
@@ -404,7 +429,7 @@ mod tests {
             Message { level: 1, duration: Duration::from_millis(2), message: "bar".to_owned() },
             Message { level: 0, duration: Duration::from_millis(5), message: "foo".to_owned() },
         ];
-        print(0, &msgs, &mut result, Duration::from_millis(0), Some(Duration::from_millis(1)));
+        print(&msgs, Duration::from_millis(0), &mut result);
         assert_eq!(
             std::str::from_utf8(&result).unwrap().lines().collect::<Vec<_>>(),
             vec![
@@ -426,7 +451,7 @@ mod tests {
             Message { level: 1, duration: Duration::from_millis(4), message: "bar".to_owned() },
             Message { level: 0, duration: Duration::from_millis(9), message: "foo".to_owned() },
         ];
-        print(0, &msgs, &mut result, Duration::from_millis(0), None);
+        print(&msgs, Duration::from_millis(0), &mut result);
         assert_eq!(
             std::str::from_utf8(&result).unwrap().lines().collect::<Vec<_>>(),
             vec![
diff --git a/crates/test_utils/src/lib.rs b/crates/test_utils/src/lib.rs
index 659f77b71..336c594a6 100644
--- a/crates/test_utils/src/lib.rs
+++ b/crates/test_utils/src/lib.rs
@@ -21,6 +21,12 @@ pub use difference::Changeset as __Changeset;
 
 pub const CURSOR_MARKER: &str = "<|>";
 
+/// Asserts that two strings are equal, otherwise displays a rich diff between them.
+///
+/// The diff shows changes from the "original" left string to the "actual" right string.
+///
+/// All arguments starting from and including the 3rd one are passed to
+/// `eprintln!()` macro in case of text inequality.
 #[macro_export]
 macro_rules! assert_eq_text {
     ($left:expr, $right:expr) => {
@@ -42,6 +48,7 @@ macro_rules! assert_eq_text {
     }};
 }
 
+/// Infallible version of `try_extract_offset()`.
 pub fn extract_offset(text: &str) -> (TextUnit, String) {
     match try_extract_offset(text) {
         None => panic!("text should contain cursor marker"),
@@ -49,6 +56,8 @@ pub fn extract_offset(text: &str) -> (TextUnit, String) {
     }
 }
 
+/// Returns the offset of the first occurence of `<|>` marker and the copy of `text`
+/// without the marker.
 fn try_extract_offset(text: &str) -> Option<(TextUnit, String)> {
     let cursor_pos = text.find(CURSOR_MARKER)?;
     let mut new_text = String::with_capacity(text.len() - CURSOR_MARKER.len());
@@ -58,6 +67,7 @@ fn try_extract_offset(text: &str) -> Option<(TextUnit, String)> {
     Some((cursor_pos, new_text))
 }
 
+/// Infallible version of `try_extract_range()`.
 pub fn extract_range(text: &str) -> (TextRange, String) {
     match try_extract_range(text) {
         None => panic!("text should contain cursor marker"),
@@ -65,6 +75,8 @@ pub fn extract_range(text: &str) -> (TextRange, String) {
     }
 }
 
+/// Returns `TextRange` between the first two markers `<|>...<|>` and the copy
+/// of `text` without both of these markers.
 fn try_extract_range(text: &str) -> Option<(TextRange, String)> {
     let (start, text) = try_extract_offset(text)?;
     let (end, text) = try_extract_offset(&text)?;
@@ -85,6 +97,11 @@ impl From<RangeOrOffset> for TextRange {
     }
 }
 
+/// Extracts `TextRange` or `TextUnit` depending on the amount of `<|>` markers
+/// found in `text`.
+///
+/// # Panics
+/// Panics if no `<|>` marker is present in the `text`.
 pub fn extract_range_or_offset(text: &str) -> (RangeOrOffset, String) {
     if let Some((range, text)) = try_extract_range(text) {
         return (RangeOrOffset::Range(range), text);
@@ -93,7 +110,7 @@ pub fn extract_range_or_offset(text: &str) -> (RangeOrOffset, String) {
     (RangeOrOffset::Offset(offset), text)
 }
 
-/// Extracts ranges, marked with `<tag> </tag>` paris from the `text`
+/// Extracts ranges, marked with `<tag> </tag>` pairs from the `text`
 pub fn extract_ranges(mut text: &str, tag: &str) -> (Vec<TextRange>, String) {
     let open = format!("<{}>", tag);
     let close = format!("</{}>", tag);
@@ -127,9 +144,9 @@ pub fn extract_ranges(mut text: &str, tag: &str) -> (Vec<TextRange>, String) {
     (ranges, res)
 }
 
+/// Inserts `<|>` marker into the `text` at `offset`.
 pub fn add_cursor(text: &str, offset: TextUnit) -> String {
-    let offset: u32 = offset.into();
-    let offset: usize = offset as usize;
+    let offset: usize = offset.to_usize();
     let mut res = String::new();
     res.push_str(&text[..offset]);
     res.push_str("<|>");
@@ -152,19 +169,6 @@ pub struct FixtureEntry {
 ///  // - other meta
 ///  ```
 pub fn parse_fixture(fixture: &str) -> Vec<FixtureEntry> {
-    let mut res = Vec::new();
-    let mut buf = String::new();
-    let mut meta: Option<&str> = None;
-
-    macro_rules! flush {
-        () => {
-            if let Some(meta) = meta {
-                res.push(FixtureEntry { meta: meta.to_string(), text: buf.clone() });
-                buf.clear();
-            }
-        };
-    };
-
     let margin = fixture
         .lines()
         .filter(|it| it.trim_start().starts_with("//-"))
@@ -172,7 +176,7 @@ pub fn parse_fixture(fixture: &str) -> Vec<FixtureEntry> {
         .next()
         .expect("empty fixture");
 
-    let lines = fixture
+    let mut lines = fixture
         .split('\n') // don't use `.lines` to not drop `\r\n`
         .filter_map(|line| {
             if line.len() >= margin {
@@ -184,17 +188,16 @@ pub fn parse_fixture(fixture: &str) -> Vec<FixtureEntry> {
             }
         });
 
-    for line in lines {
+    let mut res: Vec<FixtureEntry> = Vec::new();
+    for line in lines.by_ref() {
         if line.starts_with("//-") {
-            flush!();
-            buf.clear();
-            meta = Some(line["//-".len()..].trim());
-            continue;
+            let meta = line["//-".len()..].trim().to_string();
+            res.push(FixtureEntry { meta, text: String::new() })
+        } else if let Some(entry) = res.last_mut() {
+            entry.text.push_str(line);
+            entry.text.push('\n');
         }
-        buf.push_str(line);
-        buf.push('\n');
     }
-    flush!();
     res
 }
 
@@ -236,11 +239,10 @@ fn lines_match_works() {
     assert!(!lines_match("b", "cb"));
 }
 
-// Compares JSON object for approximate equality.
-// You can use `[..]` wildcard in strings (useful for OS dependent things such
-// as paths).  You can use a `"{...}"` string literal as a wildcard for
-// arbitrary nested JSON (useful for parts of object emitted by other programs
-// (e.g. rustc) rather than Cargo itself).  Arrays are sorted before comparison.
+/// Compares JSON object for approximate equality.
+/// You can use `[..]` wildcard in strings (useful for OS dependent things such
+/// as paths). You can use a `"{...}"` string literal as a wildcard for
+/// arbitrary nested JSON. Arrays are sorted before comparison.
 pub fn find_mismatch<'a>(expected: &'a Value, actual: &'a Value) -> Option<(&'a Value, &'a Value)> {
     use serde_json::Value::*;
     match (expected, actual) {
@@ -286,6 +288,14 @@ pub fn find_mismatch<'a>(expected: &'a Value, actual: &'a Value) -> Option<(&'a
     }
 }
 
+/// Calls callback `f` with input code and file paths of all `.rs` files from `test_data_dir`
+/// subdirectories defined by `paths`.
+///
+/// If the content of the matching `.txt` file differs from the output of `f()`
+/// the test will fail.
+///
+/// If there is no matching `.txt` file it will be created and filled with the
+/// output of `f()`, but the test will fail.
 pub fn dir_tests<F>(test_data_dir: &Path, paths: &[&str], f: F)
 where
     F: Fn(&str, &Path) -> String,
@@ -307,6 +317,7 @@ where
     }
 }
 
+/// Collects all `.rs` files from `test_data_dir` subdirectories defined by `paths`.
 pub fn collect_tests(test_data_dir: &Path, paths: &[&str]) -> Vec<(PathBuf, String)> {
     paths
         .iter()
@@ -321,6 +332,7 @@ pub fn collect_tests(test_data_dir: &Path, paths: &[&str]) -> Vec<(PathBuf, Stri
         .collect()
 }
 
+/// Collects paths to all `.rs` files from `dir` in a sorted `Vec<PathBuf>`.
 fn test_from_dir(dir: &Path) -> Vec<PathBuf> {
     let mut acc = Vec::new();
     for file in fs::read_dir(&dir).unwrap() {
@@ -334,6 +346,7 @@ fn test_from_dir(dir: &Path) -> Vec<PathBuf> {
     acc
 }
 
+/// Returns the path to the root directory of `rust-analyzer` project.
 pub fn project_dir() -> PathBuf {
     let dir = env!("CARGO_MANIFEST_DIR");
     PathBuf::from(dir).parent().unwrap().parent().unwrap().to_owned()
@@ -356,6 +369,9 @@ pub fn read_text(path: &Path) -> String {
         .replace("\r\n", "\n")
 }
 
+/// Returns `false` if slow tests should not run, otherwise returns `true` and
+/// also creates a file at `./target/.slow_tests_cookie` which serves as a flag
+/// that slow tests did run.
 pub fn skip_slow_tests() -> bool {
     let should_skip = std::env::var("CI").is_err() && std::env::var("RUN_SLOW_TESTS").is_err();
     if should_skip {
@@ -367,8 +383,9 @@ pub fn skip_slow_tests() -> bool {
     should_skip
 }
 
-const REWRITE: bool = false;
-
+/// Asserts that `expected` and `actual` strings are equal. If they differ only
+/// in trailing or leading whitespace the test won't fail and
+/// the contents of `actual` will be written to the file located at `path`.
 fn assert_equal_text(expected: &str, actual: &str, path: &Path) {
     if expected == actual {
         return;
@@ -381,6 +398,7 @@ fn assert_equal_text(expected: &str, actual: &str, path: &Path) {
         fs::write(path, actual).unwrap();
         return;
     }
+    const REWRITE: bool = false;
     if REWRITE {
         println!("rewriting {}", pretty_path.display());
         fs::write(path, actual).unwrap();
diff --git a/crates/test_utils/src/marks.rs b/crates/test_utils/src/marks.rs
index fe1813947..f8fabfaff 100644
--- a/crates/test_utils/src/marks.rs
+++ b/crates/test_utils/src/marks.rs
@@ -1,4 +1,4 @@
-//! This module implements manually tracked test coverage, which useful for
+//! This module implements manually tracked test coverage, which is useful for
 //! quickly finding a test responsible for testing a particular bit of code.
 //!
 //! See <https://matklad.github.io/2018/06/18/a-trick-for-test-maintenance.html>