86 files changed, 2462 insertions, 551 deletions

diff --git a/.github/actions/github-release/main.js b/.github/actions/github-release/main.js
index b499cd0fd..a08e59a91 100644
--- a/.github/actions/github-release/main.js
+++ b/.github/actions/github-release/main.js
@@ -70,6 +70,7 @@ async function runOnce() {
     repo,
     name,
     tag_name: name,
+    target_commitish: sha,
     prerelease: name === 'nightly',
   });
 
diff --git a/.github/workflows/release.yaml b/.github/workflows/release.yaml
index 1ae8ed1b6..c1d56a8e0 100644
--- a/.github/workflows/release.yaml
+++ b/.github/workflows/release.yaml
@@ -79,16 +79,16 @@ jobs:
       with:
         node-version: 12.x
 
-    - run: echo "::set-env name=TAG::$(date --iso --utc)"
+    - run: echo "TAG=$(date --iso --utc)" >> $GITHUB_ENV
       if: github.ref == 'refs/heads/release'
-    - run: echo "::set-env name=TAG::nightly"
+    - run: echo "TAG=nightly" >> $GITHUB_ENV
       if: github.ref != 'refs/heads/release'
     - run: 'echo "TAG: $TAG"'
 
     - name: Checkout repository
       uses: actions/checkout@v2
 
-    - run: echo "::set-env name=HEAD_SHA::$(git rev-parse HEAD)"
+    - run: echo "HEAD_SHA=$(git rev-parse HEAD)" >> $GITHUB_ENV
     - run: 'echo "HEAD_SHA: $HEAD_SHA"'
 
     - uses: actions/download-artifact@v1
diff --git a/.gitignore b/.gitignore
index 472fe1a13..b205bf3fb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,4 @@ crates/*/target
 .vscode/settings.json
 generated_assists.adoc
 generated_features.adoc
+generated_diagnostic.adoc
diff --git a/Cargo.lock b/Cargo.lock
index 7a77ed722..65c8de719 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -128,6 +128,20 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "08c48aae112d48ed9f069b33538ea9e3e90aa263cfa3d1c24309612b1f7472de"
 
 [[package]]
+name = "call_info"
+version = "0.0.0"
+dependencies = [
+ "base_db",
+ "either",
+ "expect-test",
+ "hir",
+ "ide_db",
+ "stdx",
+ "syntax",
+ "test_utils",
+]
+
+[[package]]
 name = "cargo_metadata"
 version = "0.11.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -250,6 +264,26 @@ dependencies = [
 ]
 
 [[package]]
+name = "completion"
+version = "0.0.0"
+dependencies = [
+ "assists",
+ "base_db",
+ "call_info",
+ "expect-test",
+ "hir",
+ "ide_db",
+ "itertools",
+ "log",
+ "profile",
+ "rustc-hash",
+ "stdx",
+ "syntax",
+ "test_utils",
+ "text_edit",
+]
+
+[[package]]
 name = "const_fn"
 version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -362,9 +396,9 @@ dependencies = [
 
 [[package]]
 name = "env_logger"
-version = "0.7.1"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "44533bbbb3bb3c1fa17d9f2e4e38bbbaf8396ba82193c4cb1b6445d711445d36"
+checksum = "54532e3223c5af90a6a757c90b5c5521564b07e5e7a958681bcd2afad421cdcd"
 dependencies = [
  "log",
 ]
@@ -609,7 +643,9 @@ version = "0.0.0"
 dependencies = [
  "assists",
  "base_db",
+ "call_info",
  "cfg",
+ "completion",
  "either",
  "expect-test",
  "hir",
@@ -796,9 +832,9 @@ dependencies = [
 
 [[package]]
 name = "lsp-server"
-version = "0.4.0"
+version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ff7452ee21b8de64f10ceb4e9fee1212e1a9579cd717226613333e751676c86a"
+checksum = "9c85acaf36c53bf15da2b8b35afeea56747707261f59eb0b77229081dd72b04e"
 dependencies = [
  "crossbeam-channel 0.5.0",
  "log",
@@ -1441,18 +1477,18 @@ checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 
 [[package]]
 name = "serde"
-version = "1.0.116"
+version = "1.0.117"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96fe57af81d28386a513cbc6858332abc6117cfdb5999647c6444b8f43a370a5"
+checksum = "b88fa983de7720629c9387e9f517353ed404164b1e482c970a90c1a4aaf7dc1a"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.116"
+version = "1.0.117"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f630a6370fd8e457873b4bd2ffdae75408bc291ba72be773772a4c2a065d9ae8"
+checksum = "cbd1ae72adb44aab48f325a02444a5fc079349a8d804c1fc922aed3f7454c74e"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1532,9 +1568,9 @@ version = "0.0.0"
 
 [[package]]
 name = "syn"
-version = "1.0.44"
+version = "1.0.45"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e03e57e4fcbfe7749842d53e24ccb9aa12b7252dbe5e91d2acad31834c8b8fdd"
+checksum = "ea9c5432ff16d6152371f808fb5a871cd67368171b09bb21b43df8e4a47a3556"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1916,18 +1952,18 @@ dependencies = [
 
 [[package]]
 name = "xshell"
-version = "0.1.0"
+version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1f7f756f2faab73adb00db44db716598ab2c9e4bce4a875c053022291bd3cab4"
+checksum = "3e9bbfccbb2233e6b0473b7870d4b0811a402e9e249a5e8394e768e5a5c9c37d"
 dependencies = [
  "xshell-macros",
 ]
 
 [[package]]
 name = "xshell-macros"
-version = "0.1.0"
+version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "51b020c2f3132b34067e2f6ebc58f0f210624898713a8186b8cdb75d3b8c3001"
+checksum = "b94f1c632d730a1704b21dc551a4c74fbed713cfa59593708f94943548206134"
 
 [[package]]
 name = "xtask"
diff --git a/crates/assists/src/handlers/auto_import.rs b/crates/assists/src/handlers/auto_import.rs
index 4a7059c83..e49e641b3 100644
--- a/crates/assists/src/handlers/auto_import.rs
+++ b/crates/assists/src/handlers/auto_import.rs
@@ -6,7 +6,7 @@ use crate::{
     AssistContext, AssistId, AssistKind, Assists, GroupLabel,
 };
 
-// Feature: Import Insertion
+// Feature: Auto Import
 //
 // Using the `auto-import` assist it is possible to insert missing imports for unresolved items.
 // When inserting an import it will do so in a structured manner by keeping imports grouped,
@@ -100,7 +100,7 @@ pub(crate) fn auto_import(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
     let group = import_group_message(import_assets.import_candidate());
     let scope = ImportScope::find_insert_use_container(import_assets.syntax_under_caret(), ctx)?;
     let syntax = scope.as_syntax_node();
-    for import in proposed_imports {
+    for (import, _) in proposed_imports {
         acc.add_group(
             &group,
             AssistId("auto_import", AssistKind::QuickFix),
diff --git a/crates/assists/src/handlers/change_visibility.rs b/crates/assists/src/handlers/change_visibility.rs
index 32dc05378..22d7c95d9 100644
--- a/crates/assists/src/handlers/change_visibility.rs
+++ b/crates/assists/src/handlers/change_visibility.rs
@@ -1,7 +1,7 @@
 use syntax::{
     ast::{self, NameOwner, VisibilityOwner},
     AstNode,
-    SyntaxKind::{CONST, ENUM, FN, MODULE, STATIC, STRUCT, TRAIT, VISIBILITY},
+    SyntaxKind::{CONST, ENUM, FN, MODULE, STATIC, STRUCT, TRAIT, TYPE_ALIAS, VISIBILITY},
     T,
 };
 use test_utils::mark;
@@ -30,13 +30,20 @@ fn add_vis(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let item_keyword = ctx.token_at_offset().find(|leaf| {
         matches!(
             leaf.kind(),
-            T![const] | T![static] | T![fn] | T![mod] | T![struct] | T![enum] | T![trait]
+            T![const]
+                | T![static]
+                | T![fn]
+                | T![mod]
+                | T![struct]
+                | T![enum]
+                | T![trait]
+                | T![type]
         )
     });
 
     let (offset, target) = if let Some(keyword) = item_keyword {
         let parent = keyword.parent();
-        let def_kws = vec![CONST, STATIC, FN, MODULE, STRUCT, ENUM, TRAIT];
+        let def_kws = vec![CONST, STATIC, TYPE_ALIAS, FN, MODULE, STRUCT, ENUM, TRAIT];
         // Parent is not a definition, can't add visibility
         if !def_kws.iter().any(|&def_kw| def_kw == parent.kind()) {
             return None;
@@ -160,6 +167,11 @@ mod tests {
     }
 
     #[test]
+    fn change_visibility_type_alias() {
+        check_assist(change_visibility, "<|>type T = ();", "pub(crate) type T = ();");
+    }
+
+    #[test]
     fn change_visibility_handles_comment_attrs() {
         check_assist(
             change_visibility,
diff --git a/crates/assists/src/handlers/fill_match_arms.rs b/crates/assists/src/handlers/fill_match_arms.rs
index 676f5ad92..eda45f5b3 100644
--- a/crates/assists/src/handlers/fill_match_arms.rs
+++ b/crates/assists/src/handlers/fill_match_arms.rs
@@ -59,7 +59,7 @@ pub(crate) fn fill_match_arms(acc: &mut Assists, ctx: &AssistContext) -> Option<
             .filter(|variant_pat| is_variant_missing(&mut arms, variant_pat))
             .map(|pat| make::match_arm(iter::once(pat), make::expr_empty_block()))
             .collect::<Vec<_>>();
-        if Some(enum_def) == FamousDefs(&ctx.sema, module.krate()).core_option_Option() {
+        if Some(enum_def) == FamousDefs(&ctx.sema, Some(module.krate())).core_option_Option() {
             // Match `Some` variant first.
             mark::hit!(option_order);
             variants.reverse()
diff --git a/crates/assists/src/handlers/fix_visibility.rs b/crates/assists/src/handlers/fix_visibility.rs
index d505e9444..66f74150c 100644
--- a/crates/assists/src/handlers/fix_visibility.rs
+++ b/crates/assists/src/handlers/fix_visibility.rs
@@ -1,9 +1,11 @@
 use base_db::FileId;
 use hir::{db::HirDatabase, HasSource, HasVisibility, PathResolution};
-use syntax::{ast, AstNode, TextRange, TextSize};
+use syntax::{
+    ast::{self, VisibilityOwner},
+    AstNode, TextRange, TextSize,
+};
 
 use crate::{utils::vis_offset, AssistContext, AssistId, AssistKind, Assists};
-use ast::VisibilityOwner;
 
 // FIXME: this really should be a fix for diagnostic, rather than an assist.
 
diff --git a/crates/assists/src/handlers/generate_from_impl_for_enum.rs b/crates/assists/src/handlers/generate_from_impl_for_enum.rs
index 7f04b9572..674e5a175 100644
--- a/crates/assists/src/handlers/generate_from_impl_for_enum.rs
+++ b/crates/assists/src/handlers/generate_from_impl_for_enum.rs
@@ -75,7 +75,7 @@ fn existing_from_impl(
     let enum_ = variant.parent_enum(sema.db);
     let krate = enum_.module(sema.db).krate();
 
-    let from_trait = FamousDefs(sema, krate).core_convert_From()?;
+    let from_trait = FamousDefs(sema, Some(krate)).core_convert_From()?;
 
     let enum_type = enum_.ty(sema.db);
 
diff --git a/crates/assists/src/handlers/qualify_path.rs b/crates/assists/src/handlers/qualify_path.rs
new file mode 100644
index 000000000..f436bdbbf
--- /dev/null
+++ b/crates/assists/src/handlers/qualify_path.rs
@@ -0,0 +1,1048 @@
+use std::iter;
+
+use hir::AsName;
+use ide_db::RootDatabase;
+use syntax::{
+    ast,
+    ast::{make, ArgListOwner},
+    AstNode,
+};
+use test_utils::mark;
+
+use crate::{
+    assist_context::{AssistContext, Assists},
+    utils::import_assets::{ImportAssets, ImportCandidate},
+    utils::mod_path_to_ast,
+    AssistId, AssistKind, GroupLabel,
+};
+
+// Assist: qualify_path
+//
+// If the name is unresolved, provides all possible qualified paths for it.
+//
+// ```
+// fn main() {
+//     let map = HashMap<|>::new();
+// }
+// # pub mod std { pub mod collections { pub struct HashMap { } } }
+// ```
+// ->
+// ```
+// fn main() {
+//     let map = std::collections::HashMap::new();
+// }
+// # pub mod std { pub mod collections { pub struct HashMap { } } }
+// ```
+pub(crate) fn qualify_path(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let import_assets =
+        if let Some(path_under_caret) = ctx.find_node_at_offset_with_descend::<ast::Path>() {
+            ImportAssets::for_regular_path(path_under_caret, &ctx.sema)
+        } else if let Some(method_under_caret) =
+            ctx.find_node_at_offset_with_descend::<ast::MethodCallExpr>()
+        {
+            ImportAssets::for_method_call(method_under_caret, &ctx.sema)
+        } else {
+            None
+        }?;
+    let proposed_imports = import_assets.search_for_relative_paths(&ctx.sema);
+    if proposed_imports.is_empty() {
+        return None;
+    }
+
+    let candidate = import_assets.import_candidate();
+    let range = ctx.sema.original_range(import_assets.syntax_under_caret()).range;
+
+    let qualify_candidate = match candidate {
+        ImportCandidate::QualifierStart(_) => {
+            mark::hit!(qualify_path_qualifier_start);
+            let path = ast::Path::cast(import_assets.syntax_under_caret().clone())?;
+            let segment = path.segment()?;
+            QualifyCandidate::QualifierStart(segment)
+        }
+        ImportCandidate::UnqualifiedName(_) => {
+            mark::hit!(qualify_path_unqualified_name);
+            QualifyCandidate::UnqualifiedName
+        }
+        ImportCandidate::TraitAssocItem(_) => {
+            mark::hit!(qualify_path_trait_assoc_item);
+            let path = ast::Path::cast(import_assets.syntax_under_caret().clone())?;
+            let (qualifier, segment) = (path.qualifier()?, path.segment()?);
+            QualifyCandidate::TraitAssocItem(qualifier, segment)
+        }
+        ImportCandidate::TraitMethod(_) => {
+            mark::hit!(qualify_path_trait_method);
+            let mcall_expr = ast::MethodCallExpr::cast(import_assets.syntax_under_caret().clone())?;
+            QualifyCandidate::TraitMethod(ctx.sema.db, mcall_expr)
+        }
+    };
+
+    let group_label = group_label(candidate);
+    for (import, item) in proposed_imports {
+        acc.add_group(
+            &group_label,
+            AssistId("qualify_path", AssistKind::QuickFix),
+            label(candidate, &import),
+            range,
+            |builder| {
+                qualify_candidate.qualify(
+                    |replace_with: String| builder.replace(range, replace_with),
+                    import,
+                    item,
+                )
+            },
+        );
+    }
+    Some(())
+}
+
+enum QualifyCandidate<'db> {
+    QualifierStart(ast::PathSegment),
+    UnqualifiedName,
+    TraitAssocItem(ast::Path, ast::PathSegment),
+    TraitMethod(&'db RootDatabase, ast::MethodCallExpr),
+}
+
+impl QualifyCandidate<'_> {
+    fn qualify(&self, mut replacer: impl FnMut(String), import: hir::ModPath, item: hir::ItemInNs) {
+        match self {
+            QualifyCandidate::QualifierStart(segment) => {
+                let import = mod_path_to_ast(&import);
+                replacer(format!("{}::{}", import, segment));
+            }
+            QualifyCandidate::UnqualifiedName => replacer(mod_path_to_ast(&import).to_string()),
+            QualifyCandidate::TraitAssocItem(qualifier, segment) => {
+                let import = mod_path_to_ast(&import);
+                replacer(format!("<{} as {}>::{}", qualifier, import, segment));
+            }
+            &QualifyCandidate::TraitMethod(db, ref mcall_expr) => {
+                Self::qualify_trait_method(db, mcall_expr, replacer, import, item);
+            }
+        }
+    }
+
+    fn qualify_trait_method(
+        db: &RootDatabase,
+        mcall_expr: &ast::MethodCallExpr,
+        mut replacer: impl FnMut(String),
+        import: hir::ModPath,
+        item: hir::ItemInNs,
+    ) -> Option<()> {
+        let receiver = mcall_expr.receiver()?;
+        let trait_method_name = mcall_expr.name_ref()?;
+        let arg_list = mcall_expr.arg_list().map(|arg_list| arg_list.args());
+        let trait_ = item_as_trait(item)?;
+        let method = find_trait_method(db, trait_, &trait_method_name)?;
+        if let Some(self_access) = method.self_param(db).map(|sp| sp.access(db)) {
+            let import = mod_path_to_ast(&import);
+            let receiver = match self_access {
+                hir::Access::Shared => make::expr_ref(receiver, false),
+                hir::Access::Exclusive => make::expr_ref(receiver, true),
+                hir::Access::Owned => receiver,
+            };
+            replacer(format!(
+                "{}::{}{}",
+                import,
+                trait_method_name,
+                match arg_list.clone() {
+                    Some(args) => make::arg_list(iter::once(receiver).chain(args)),
+                    None => make::arg_list(iter::once(receiver)),
+                }
+            ));
+        }
+        Some(())
+    }
+}
+
+fn find_trait_method(
+    db: &RootDatabase,
+    trait_: hir::Trait,
+    trait_method_name: &ast::NameRef,
+) -> Option<hir::Function> {
+    if let Some(hir::AssocItem::Function(method)) =
+        trait_.items(db).into_iter().find(|item: &hir::AssocItem| {
+            item.name(db).map(|name| name == trait_method_name.as_name()).unwrap_or(false)
+        })
+    {
+        Some(method)
+    } else {
+        None
+    }
+}
+
+fn item_as_trait(item: hir::ItemInNs) -> Option<hir::Trait> {
+    if let hir::ModuleDef::Trait(trait_) = hir::ModuleDef::from(item.as_module_def_id()?) {
+        Some(trait_)
+    } else {
+        None
+    }
+}
+
+fn group_label(candidate: &ImportCandidate) -> GroupLabel {
+    let name = match candidate {
+        ImportCandidate::UnqualifiedName(it) | ImportCandidate::QualifierStart(it) => &it.name,
+        ImportCandidate::TraitAssocItem(it) | ImportCandidate::TraitMethod(it) => &it.name,
+    };
+    GroupLabel(format!("Qualify {}", name))
+}
+
+fn label(candidate: &ImportCandidate, import: &hir::ModPath) -> String {
+    match candidate {
+        ImportCandidate::UnqualifiedName(_) => format!("Qualify as `{}`", &import),
+        ImportCandidate::QualifierStart(_) => format!("Qualify with `{}`", &import),
+        ImportCandidate::TraitAssocItem(_) => format!("Qualify `{}`", &import),
+        ImportCandidate::TraitMethod(_) => format!("Qualify with cast as `{}`", &import),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable, check_assist_target};
+
+    use super::*;
+
+    #[test]
+    fn applicable_when_found_an_import_partial() {
+        mark::check!(qualify_path_unqualified_name);
+        check_assist(
+            qualify_path,
+            r"
+            mod std {
+                pub mod fmt {
+                    pub struct Formatter;
+                }
+            }
+
+            use std::fmt;
+
+            <|>Formatter
+            ",
+            r"
+            mod std {
+                pub mod fmt {
+                    pub struct Formatter;
+                }
+            }
+
+            use std::fmt;
+
+            fmt::Formatter
+            ",
+        );
+    }
+
+    #[test]
+    fn applicable_when_found_an_import() {
+        check_assist(
+            qualify_path,
+            r"
+            <|>PubStruct
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+            r"
+            PubMod::PubStruct
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn applicable_in_macros() {
+        check_assist(
+            qualify_path,
+            r"
+            macro_rules! foo {
+                ($i:ident) => { fn foo(a: $i) {} }
+            }
+            foo!(Pub<|>Struct);
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+            r"
+            macro_rules! foo {
+                ($i:ident) => { fn foo(a: $i) {} }
+            }
+            foo!(PubMod::PubStruct);
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn applicable_when_found_multiple_imports() {
+        check_assist(
+            qualify_path,
+            r"
+            PubSt<|>ruct
+
+            pub mod PubMod1 {
+                pub struct PubStruct;
+            }
+            pub mod PubMod2 {
+                pub struct PubStruct;
+            }
+            pub mod PubMod3 {
+                pub struct PubStruct;
+            }
+            ",
+            r"
+            PubMod3::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_not_applicable(
+            qualify_path,
+            r"
+            use PubMod::PubStruct;
+
+            PubStruct<|>
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_types_with_private_paths() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            PrivateStruct<|>
+
+            pub mod PubMod {
+                struct PrivateStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_when_no_imports_found() {
+        check_assist_not_applicable(
+            qualify_path,
+            "
+            PubStruct<|>",
+        );
+    }
+
+    #[test]
+    fn not_applicable_in_import_statements() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            use PubStruct<|>;
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }",
+        );
+    }
+
+    #[test]
+    fn qualify_function() {
+        check_assist(
+            qualify_path,
+            r"
+            test_function<|>
+
+            pub mod PubMod {
+                pub fn test_function() {};
+            }
+            ",
+            r"
+            PubMod::test_function
+
+            pub mod PubMod {
+                pub fn test_function() {};
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn qualify_macro() {
+        check_assist(
+            qualify_path,
+            r"
+//- /lib.rs crate:crate_with_macro
+#[macro_export]
+macro_rules! foo {
+    () => ()
+}
+
+//- /main.rs crate:main deps:crate_with_macro
+fn main() {
+    foo<|>
+}
+",
+            r"
+fn main() {
+    crate_with_macro::foo
+}
+",
+        );
+    }
+
+    #[test]
+    fn qualify_path_target() {
+        check_assist_target(
+            qualify_path,
+            r"
+            struct AssistInfo {
+                group_label: Option<<|>GroupLabel>,
+            }
+
+            mod m { pub struct GroupLabel; }
+            ",
+            "GroupLabel",
+        )
+    }
+
+    #[test]
+    fn not_applicable_when_path_start_is_imported() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            pub mod mod1 {
+                pub mod mod2 {
+                    pub mod mod3 {
+                        pub struct TestStruct;
+                    }
+                }
+            }
+
+            use mod1::mod2;
+            fn main() {
+                mod2::mod3::TestStruct<|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_imported_function() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            pub mod test_mod {
+                pub fn test_function() {}
+            }
+
+            use test_mod::test_function;
+            fn main() {
+                test_function<|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn associated_struct_function() {
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub struct TestStruct {}
+                impl TestStruct {
+                    pub fn test_function() {}
+                }
+            }
+
+            fn main() {
+                TestStruct::test_function<|>
+            }
+            ",
+            r"
+            mod test_mod {
+                pub struct TestStruct {}
+                impl TestStruct {
+                    pub fn test_function() {}
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::test_function
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn associated_struct_const() {
+        mark::check!(qualify_path_qualifier_start);
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub struct TestStruct {}
+                impl TestStruct {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                TestStruct::TEST_CONST<|>
+            }
+            ",
+            r"
+            mod test_mod {
+                pub struct TestStruct {}
+                impl TestStruct {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::TEST_CONST
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn associated_trait_function() {
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_function();
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_function() {}
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::test_function<|>
+            }
+            ",
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_function();
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_function() {}
+                }
+            }
+
+            fn main() {
+                <test_mod::TestStruct as test_mod::TestTrait>::test_function
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_imported_trait_for_function() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_function();
+                }
+                pub trait TestTrait2 {
+                    fn test_function();
+                }
+                pub enum TestEnum {
+                    One,
+                    Two,
+                }
+                impl TestTrait2 for TestEnum {
+                    fn test_function() {}
+                }
+                impl TestTrait for TestEnum {
+                    fn test_function() {}
+                }
+            }
+
+            use test_mod::TestTrait2;
+            fn main() {
+                test_mod::TestEnum::test_function<|>;
+            }
+            ",
+        )
+    }
+
+    #[test]
+    fn associated_trait_const() {
+        mark::check!(qualify_path_trait_assoc_item);
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    const TEST_CONST: u8;
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::TEST_CONST<|>
+            }
+            ",
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    const TEST_CONST: u8;
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                <test_mod::TestStruct as test_mod::TestTrait>::TEST_CONST
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_imported_trait_for_const() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    const TEST_CONST: u8;
+                }
+                pub trait TestTrait2 {
+                    const TEST_CONST: f64;
+                }
+                pub enum TestEnum {
+                    One,
+                    Two,
+                }
+                impl TestTrait2 for TestEnum {
+                    const TEST_CONST: f64 = 42.0;
+                }
+                impl TestTrait for TestEnum {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            use test_mod::TestTrait2;
+            fn main() {
+                test_mod::TestEnum::TEST_CONST<|>;
+            }
+            ",
+        )
+    }
+
+    #[test]
+    fn trait_method() {
+        mark::check!(qualify_path_trait_method);
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(&self) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_struct.test_meth<|>od()
+            }
+            ",
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(&self) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_mod::TestTrait::test_method(&test_struct)
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn trait_method_multi_params() {
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self, test: i32);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(&self, test: i32) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_struct.test_meth<|>od(42)
+            }
+            ",
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self, test: i32);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(&self, test: i32) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_mod::TestTrait::test_method(&test_struct, 42)
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn trait_method_consume() {
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(self) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_struct.test_meth<|>od()
+            }
+            ",
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(self) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_mod::TestTrait::test_method(test_struct)
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn trait_method_cross_crate() {
+        check_assist(
+            qualify_path,
+            r"
+            //- /main.rs crate:main deps:dep
+            fn main() {
+                let test_struct = dep::test_mod::TestStruct {};
+                test_struct.test_meth<|>od()
+            }
+            //- /dep.rs crate:dep
+            pub mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(&self) {}
+                }
+            }
+            ",
+            r"
+            fn main() {
+                let test_struct = dep::test_mod::TestStruct {};
+                dep::test_mod::TestTrait::test_method(&test_struct)
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn assoc_fn_cross_crate() {
+        check_assist(
+            qualify_path,
+            r"
+            //- /main.rs crate:main deps:dep
+            fn main() {
+                dep::test_mod::TestStruct::test_func<|>tion
+            }
+            //- /dep.rs crate:dep
+            pub mod test_mod {
+                pub trait TestTrait {
+                    fn test_function();
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_function() {}
+                }
+            }
+            ",
+            r"
+            fn main() {
+                <dep::test_mod::TestStruct as dep::test_mod::TestTrait>::test_function
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn assoc_const_cross_crate() {
+        check_assist(
+            qualify_path,
+            r"
+            //- /main.rs crate:main deps:dep
+            fn main() {
+                dep::test_mod::TestStruct::CONST<|>
+            }
+            //- /dep.rs crate:dep
+            pub mod test_mod {
+                pub trait TestTrait {
+                    const CONST: bool;
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    const CONST: bool = true;
+                }
+            }
+            ",
+            r"
+            fn main() {
+                <dep::test_mod::TestStruct as dep::test_mod::TestTrait>::CONST
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn assoc_fn_as_method_cross_crate() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            //- /main.rs crate:main deps:dep
+            fn main() {
+                let test_struct = dep::test_mod::TestStruct {};
+                test_struct.test_func<|>tion()
+            }
+            //- /dep.rs crate:dep
+            pub mod test_mod {
+                pub trait TestTrait {
+                    fn test_function();
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_function() {}
+                }
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn private_trait_cross_crate() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            //- /main.rs crate:main deps:dep
+            fn main() {
+                let test_struct = dep::test_mod::TestStruct {};
+                test_struct.test_meth<|>od()
+            }
+            //- /dep.rs crate:dep
+            pub mod test_mod {
+                trait TestTrait {
+                    fn test_method(&self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(&self) {}
+                }
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_imported_trait_for_method() {
+        check_assist_not_applicable(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self);
+                }
+                pub trait TestTrait2 {
+                    fn test_method(&self);
+                }
+                pub enum TestEnum {
+                    One,
+                    Two,
+                }
+                impl TestTrait2 for TestEnum {
+                    fn test_method(&self) {}
+                }
+                impl TestTrait for TestEnum {
+                    fn test_method(&self) {}
+                }
+            }
+
+            use test_mod::TestTrait2;
+            fn main() {
+                let one = test_mod::TestEnum::One;
+                one.test<|>_method();
+            }
+            ",
+        )
+    }
+
+    #[test]
+    fn dep_import() {
+        check_assist(
+            qualify_path,
+            r"
+//- /lib.rs crate:dep
+pub struct Struct;
+
+//- /main.rs crate:main deps:dep
+fn main() {
+    Struct<|>
+}
+",
+            r"
+fn main() {
+    dep::Struct
+}
+",
+        );
+    }
+
+    #[test]
+    fn whole_segment() {
+        // Tests that only imports whose last segment matches the identifier get suggested.
+        check_assist(
+            qualify_path,
+            r"
+//- /lib.rs crate:dep
+pub mod fmt {
+    pub trait Display {}
+}
+
+pub fn panic_fmt() {}
+
+//- /main.rs crate:main deps:dep
+struct S;
+
+impl f<|>mt::Display for S {}
+",
+            r"
+struct S;
+
+impl dep::fmt::Display for S {}
+",
+        );
+    }
+
+    #[test]
+    fn macro_generated() {
+        // Tests that macro-generated items are suggested from external crates.
+        check_assist(
+            qualify_path,
+            r"
+//- /lib.rs crate:dep
+macro_rules! mac {
+    () => {
+        pub struct Cheese;
+    };
+}
+
+mac!();
+
+//- /main.rs crate:main deps:dep
+fn main() {
+    Cheese<|>;
+}
+",
+            r"
+fn main() {
+    dep::Cheese;
+}
+",
+        );
+    }
+
+    #[test]
+    fn casing() {
+        // Tests that differently cased names don't interfere and we only suggest the matching one.
+        check_assist(
+            qualify_path,
+            r"
+//- /lib.rs crate:dep
+pub struct FMT;
+pub struct fmt;
+
+//- /main.rs crate:main deps:dep
+fn main() {
+    FMT<|>;
+}
+",
+            r"
+fn main() {
+    dep::FMT;
+}
+",
+        );
+    }
+}
diff --git a/crates/assists/src/handlers/replace_string_with_char.rs b/crates/assists/src/handlers/replace_string_with_char.rs
new file mode 100644
index 000000000..4ca87a8ec
--- /dev/null
+++ b/crates/assists/src/handlers/replace_string_with_char.rs
@@ -0,0 +1,141 @@
+use syntax::{
+    ast::{self, HasStringValue},
+    AstToken,
+    SyntaxKind::STRING,
+};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: replace_string_with_char
+//
+// Replace string with char.
+//
+// ```
+// fn main() {
+//     find("{<|>");
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     find('{');
+// }
+// ```
+pub(crate) fn replace_string_with_char(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let token = ctx.find_token_at_offset(STRING).and_then(ast::String::cast)?;
+    let value = token.value()?;
+    let target = token.syntax().text_range();
+
+    if value.chars().take(2).count() != 1 {
+        return None;
+    }
+
+    acc.add(
+        AssistId("replace_string_with_char", AssistKind::RefactorRewrite),
+        "Replace string with char",
+        target,
+        |edit| {
+            edit.replace(token.syntax().text_range(), format!("'{}'", value));
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable, check_assist_target};
+
+    use super::*;
+
+    #[test]
+    fn replace_string_with_char_target() {
+        check_assist_target(
+            replace_string_with_char,
+            r#"
+            fn f() {
+                let s = "<|>c";
+            }
+            "#,
+            r#""c""#,
+        );
+    }
+
+    #[test]
+    fn replace_string_with_char_assist() {
+        check_assist(
+            replace_string_with_char,
+            r#"
+    fn f() {
+        let s = "<|>c";
+    }
+    "#,
+            r##"
+    fn f() {
+        let s = 'c';
+    }
+    "##,
+        )
+    }
+
+    #[test]
+    fn replace_string_with_char_assist_with_emoji() {
+        check_assist(
+            replace_string_with_char,
+            r#"
+    fn f() {
+        let s = "<|>😀";
+    }
+    "#,
+            r##"
+    fn f() {
+        let s = '😀';
+    }
+    "##,
+        )
+    }
+
+    #[test]
+    fn replace_string_with_char_assist_not_applicable() {
+        check_assist_not_applicable(
+            replace_string_with_char,
+            r#"
+    fn f() {
+        let s = "<|>test";
+    }
+    "#,
+        )
+    }
+
+    #[test]
+    fn replace_string_with_char_works_inside_macros() {
+        check_assist(
+            replace_string_with_char,
+            r#"
+                fn f() {
+                    format!(<|>"x", 92)
+                }
+                "#,
+            r##"
+                fn f() {
+                    format!('x', 92)
+                }
+                "##,
+        )
+    }
+
+    #[test]
+    fn replace_string_with_char_works_func_args() {
+        check_assist(
+            replace_string_with_char,
+            r#"
+                fn f() {
+                    find(<|>"x");
+                }
+                "#,
+            r##"
+                fn f() {
+                    find('x');
+                }
+                "##,
+        )
+    }
+}
diff --git a/crates/assists/src/lib.rs b/crates/assists/src/lib.rs
index a2bec818c..8a664f654 100644
--- a/crates/assists/src/lib.rs
+++ b/crates/assists/src/lib.rs
@@ -150,6 +150,7 @@ mod handlers {
     mod merge_match_arms;
     mod move_bounds;
     mod move_guard;
+    mod qualify_path;
     mod raw_string;
     mod remove_dbg;
     mod remove_mut;
@@ -159,6 +160,7 @@ mod handlers {
     mod replace_impl_trait_with_generic;
     mod replace_let_with_if_let;
     mod replace_qualified_name_with_use;
+    mod replace_string_with_char;
     mod replace_unwrap_with_match;
     mod split_import;
     mod unwrap_block;
@@ -196,6 +198,7 @@ mod handlers {
             move_bounds::move_bounds_to_where_clause,
             move_guard::move_arm_cond_to_match_guard,
             move_guard::move_guard_to_arm_body,
+            qualify_path::qualify_path,
             raw_string::add_hash,
             raw_string::make_raw_string,
             raw_string::make_usual_string,
@@ -208,6 +211,7 @@ mod handlers {
             replace_impl_trait_with_generic::replace_impl_trait_with_generic,
             replace_let_with_if_let::replace_let_with_if_let,
             replace_qualified_name_with_use::replace_qualified_name_with_use,
+            replace_string_with_char::replace_string_with_char,
             replace_unwrap_with_match::replace_unwrap_with_match,
             split_import::split_import,
             unwrap_block::unwrap_block,
diff --git a/crates/assists/src/tests/generated.rs b/crates/assists/src/tests/generated.rs
index 41f536574..acbf5b652 100644
--- a/crates/assists/src/tests/generated.rs
+++ b/crates/assists/src/tests/generated.rs
@@ -713,6 +713,25 @@ fn handle(action: Action) {
 }
 
 #[test]
+fn doctest_qualify_path() {
+    check_doc_test(
+        "qualify_path",
+        r#####"
+fn main() {
+    let map = HashMap<|>::new();
+}
+pub mod std { pub mod collections { pub struct HashMap { } } }
+"#####,
+        r#####"
+fn main() {
+    let map = std::collections::HashMap::new();
+}
+pub mod std { pub mod collections { pub struct HashMap { } } }
+"#####,
+    )
+}
+
+#[test]
 fn doctest_remove_dbg() {
     check_doc_test(
         "remove_dbg",
@@ -882,6 +901,23 @@ fn process(map: HashMap<String, String>) {}
 }
 
 #[test]
+fn doctest_replace_string_with_char() {
+    check_doc_test(
+        "replace_string_with_char",
+        r#####"
+fn main() {
+    find("{<|>");
+}
+"#####,
+        r#####"
+fn main() {
+    find('{');
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_replace_unwrap_with_match() {
     check_doc_test(
         "replace_unwrap_with_match",
diff --git a/crates/assists/src/utils.rs b/crates/assists/src/utils.rs
index b37b0d2b6..1a6b48b45 100644
--- a/crates/assists/src/utils.rs
+++ b/crates/assists/src/utils.rs
@@ -275,7 +275,7 @@ impl TryEnum {
 /// somewhat similar to the known paths infra inside hir, but it different; We
 /// want to make sure that IDE specific paths don't become interesting inside
 /// the compiler itself as well.
-pub struct FamousDefs<'a, 'b>(pub &'a Semantics<'b, RootDatabase>, pub Crate);
+pub struct FamousDefs<'a, 'b>(pub &'a Semantics<'b, RootDatabase>, pub Option<Crate>);
 
 #[allow(non_snake_case)]
 impl FamousDefs<'_, '_> {
@@ -362,6 +362,10 @@ pub mod prelude {
 pub use prelude::*;
 "#;
 
+    pub fn core(&self) -> Option<Crate> {
+        self.find_crate("core")
+    }
+
     pub(crate) fn core_convert_From(&self) -> Option<Trait> {
         self.find_trait("core:convert:From")
     }
@@ -399,21 +403,20 @@ pub use prelude::*;
         }
     }
 
+    fn find_crate(&self, name: &str) -> Option<Crate> {
+        let krate = self.1?;
+        let db = self.0.db;
+        let res =
+            krate.dependencies(db).into_iter().find(|dep| dep.name.to_string() == name)?.krate;
+        Some(res)
+    }
+
     fn find_def(&self, path: &str) -> Option<ScopeDef> {
         let db = self.0.db;
         let mut path = path.split(':');
         let trait_ = path.next_back()?;
         let std_crate = path.next()?;
-        let std_crate = if self
-            .1
-            .declaration_name(db)
-            .map(|name| name.to_string() == std_crate)
-            .unwrap_or(false)
-        {
-            self.1
-        } else {
-            self.1.dependencies(db).into_iter().find(|dep| dep.name.to_string() == std_crate)?.krate
-        };
+        let std_crate = self.find_crate(std_crate)?;
         let mut module = std_crate.root_module(db);
         for segment in path {
             module = module.children(db).find_map(|child| {
diff --git a/crates/assists/src/utils/import_assets.rs b/crates/assists/src/utils/import_assets.rs
index 601f51098..23db3a74b 100644
--- a/crates/assists/src/utils/import_assets.rs
+++ b/crates/assists/src/utils/import_assets.rs
@@ -1,6 +1,4 @@
 //! Look up accessible paths for items.
-use std::collections::BTreeSet;
-
 use either::Either;
 use hir::{AsAssocItem, AssocItemContainer, ModuleDef, Semantics};
 use ide_db::{imports_locator, RootDatabase};
@@ -29,12 +27,12 @@ pub(crate) enum ImportCandidate {
 #[derive(Debug)]
 pub(crate) struct TraitImportCandidate {
     pub ty: hir::Type,
-    pub name: String,
+    pub name: ast::NameRef,
 }
 
 #[derive(Debug)]
 pub(crate) struct PathImportCandidate {
-    pub name: String,
+    pub name: ast::NameRef,
 }
 
 #[derive(Debug)]
@@ -86,9 +84,9 @@ impl ImportAssets {
     fn get_search_query(&self) -> &str {
         match &self.import_candidate {
             ImportCandidate::UnqualifiedName(candidate)
-            | ImportCandidate::QualifierStart(candidate) => &candidate.name,
+            | ImportCandidate::QualifierStart(candidate) => candidate.name.text(),
             ImportCandidate::TraitAssocItem(candidate)
-            | ImportCandidate::TraitMethod(candidate) => &candidate.name,
+            | ImportCandidate::TraitMethod(candidate) => candidate.name.text(),
         }
     }
 
@@ -96,7 +94,7 @@ impl ImportAssets {
         &self,
         sema: &Semantics<RootDatabase>,
         config: &InsertUseConfig,
-    ) -> BTreeSet<hir::ModPath> {
+    ) -> Vec<(hir::ModPath, hir::ItemInNs)> {
         let _p = profile::span("import_assists::search_for_imports");
         self.search_for(sema, Some(config.prefix_kind))
     }
@@ -106,7 +104,7 @@ impl ImportAssets {
     pub(crate) fn search_for_relative_paths(
         &self,
         sema: &Semantics<RootDatabase>,
-    ) -> BTreeSet<hir::ModPath> {
+    ) -> Vec<(hir::ModPath, hir::ItemInNs)> {
         let _p = profile::span("import_assists::search_for_relative_paths");
         self.search_for(sema, None)
     }
@@ -115,7 +113,7 @@ impl ImportAssets {
         &self,
         sema: &Semantics<RootDatabase>,
         prefixed: Option<hir::PrefixKind>,
-    ) -> BTreeSet<hir::ModPath> {
+    ) -> Vec<(hir::ModPath, hir::ItemInNs)> {
         let db = sema.db;
         let mut trait_candidates = FxHashSet::default();
         let current_crate = self.module_with_name_to_import.krate();
@@ -181,7 +179,7 @@ impl ImportAssets {
             }
         };
 
-        imports_locator::find_imports(sema, current_crate, &self.get_search_query())
+        let mut res = imports_locator::find_imports(sema, current_crate, &self.get_search_query())
             .into_iter()
             .filter_map(filter)
             .filter_map(|candidate| {
@@ -191,10 +189,13 @@ impl ImportAssets {
                 } else {
                     self.module_with_name_to_import.find_use_path(db, item)
                 }
+                .map(|path| (path, item))
             })
-            .filter(|use_path| !use_path.segments.is_empty())
+            .filter(|(use_path, _)| !use_path.segments.is_empty())
             .take(20)
-            .collect::<BTreeSet<_>>()
+            .collect::<Vec<_>>();
+        res.sort_by_key(|(path, _)| path.clone());
+        res
     }
 
     fn assoc_to_trait(assoc: AssocItemContainer) -> Option<hir::Trait> {
@@ -215,7 +216,7 @@ impl ImportCandidate {
             Some(_) => None,
             None => Some(Self::TraitMethod(TraitImportCandidate {
                 ty: sema.type_of_expr(&method_call.receiver()?)?,
-                name: method_call.name_ref()?.syntax().to_string(),
+                name: method_call.name_ref()?,
             })),
         }
     }
@@ -243,24 +244,17 @@ impl ImportCandidate {
                     hir::PathResolution::Def(hir::ModuleDef::Adt(assoc_item_path)) => {
                         ImportCandidate::TraitAssocItem(TraitImportCandidate {
                             ty: assoc_item_path.ty(sema.db),
-                            name: segment.syntax().to_string(),
+                            name: segment.name_ref()?,
                         })
                     }
                     _ => return None,
                 }
             } else {
-                ImportCandidate::QualifierStart(PathImportCandidate {
-                    name: qualifier_start.syntax().to_string(),
-                })
+                ImportCandidate::QualifierStart(PathImportCandidate { name: qualifier_start })
             }
         } else {
             ImportCandidate::UnqualifiedName(PathImportCandidate {
-                name: segment
-                    .syntax()
-                    .descendants()
-                    .find_map(ast::NameRef::cast)?
-                    .syntax()
-                    .to_string(),
+                name: segment.syntax().descendants().find_map(ast::NameRef::cast)?,
             })
         };
         Some(candidate)
diff --git a/crates/base_db/src/fixture.rs b/crates/base_db/src/fixture.rs
index 72f1fd667..66e6443cb 100644
--- a/crates/base_db/src/fixture.rs
+++ b/crates/base_db/src/fixture.rs
@@ -158,7 +158,7 @@ impl ChangeFixture {
                 let crate_id = crate_graph.add_crate_root(
                     file_id,
                     meta.edition,
-                    Some(crate_name.clone()),
+                    Some(crate_name.clone().into()),
                     meta.cfg,
                     meta.env,
                     Default::default(),
@@ -187,7 +187,7 @@ impl ChangeFixture {
             crate_graph.add_crate_root(
                 crate_root,
                 Edition::Edition2018,
-                Some(CrateName::new("test").unwrap()),
+                Some(CrateName::new("test").unwrap().into()),
                 default_cfg,
                 Env::default(),
                 Default::default(),
diff --git a/crates/base_db/src/input.rs b/crates/base_db/src/input.rs
index 215ac4b41..87f0a0ce5 100644
--- a/crates/base_db/src/input.rs
+++ b/crates/base_db/src/input.rs
@@ -102,11 +102,46 @@ impl fmt::Display for CrateName {
 
 impl ops::Deref for CrateName {
     type Target = str;
-    fn deref(&self) -> &Self::Target {
+    fn deref(&self) -> &str {
         &*self.0
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct CrateDisplayName {
+    // The name we use to display various paths (with `_`).
+    crate_name: CrateName,
+    // The name as specified in Cargo.toml (with `-`).
+    canonical_name: String,
+}
+
+impl From<CrateName> for CrateDisplayName {
+    fn from(crate_name: CrateName) -> CrateDisplayName {
+        let canonical_name = crate_name.to_string();
+        CrateDisplayName { crate_name, canonical_name }
+    }
+}
+
+impl fmt::Display for CrateDisplayName {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.crate_name)
+    }
+}
+
+impl ops::Deref for CrateDisplayName {
+    type Target = str;
+    fn deref(&self) -> &str {
+        &*self.crate_name
+    }
+}
+
+impl CrateDisplayName {
+    pub fn from_canonical_name(canonical_name: String) -> CrateDisplayName {
+        let crate_name = CrateName::normalize_dashes(&canonical_name);
+        CrateDisplayName { crate_name, canonical_name }
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct ProcMacroId(pub u32);
 
@@ -127,11 +162,13 @@ impl PartialEq for ProcMacro {
 pub struct CrateData {
     pub root_file_id: FileId,
     pub edition: Edition,
-    /// A name used in the package's project declaration: for Cargo projects, it's [package].name,
-    /// can be different for other project types or even absent (a dummy crate for the code snippet, for example).
-    /// NOTE: The crate can be referenced as a dependency under a different name,
-    /// this one should be used when working with crate hierarchies.
-    pub declaration_name: Option<CrateName>,
+    /// A name used in the package's project declaration: for Cargo projects,
+    /// it's [package].name, can be different for other project types or even
+    /// absent (a dummy crate for the code snippet, for example).
+    ///
+    /// For purposes of analysis, crates are anonymous (only names in
+    /// `Dependency` matters), this name should only be used for UI.
+    pub display_name: Option<CrateDisplayName>,
     pub cfg_options: CfgOptions,
     pub env: Env,
     pub dependencies: Vec<Dependency>,
@@ -160,7 +197,7 @@ impl CrateGraph {
         &mut self,
         file_id: FileId,
         edition: Edition,
-        declaration_name: Option<CrateName>,
+        display_name: Option<CrateDisplayName>,
         cfg_options: CfgOptions,
         env: Env,
         proc_macro: Vec<(SmolStr, Arc<dyn tt::TokenExpander>)>,
@@ -171,7 +208,7 @@ impl CrateGraph {
         let data = CrateData {
             root_file_id: file_id,
             edition,
-            declaration_name,
+            display_name,
             cfg_options,
             env,
             proc_macro,
@@ -290,6 +327,29 @@ impl CrateGraph {
         }
         false
     }
+
+    // Work around for https://github.com/rust-analyzer/rust-analyzer/issues/6038.
+    // As hacky as it gets.
+    pub fn patch_cfg_if(&mut self) -> bool {
+        let cfg_if = self.hacky_find_crate("cfg_if");
+        let std = self.hacky_find_crate("std");
+        match (cfg_if, std) {
+            (Some(cfg_if), Some(std)) => {
+                self.arena.get_mut(&cfg_if).unwrap().dependencies.clear();
+                self.arena
+                    .get_mut(&std)
+                    .unwrap()
+                    .dependencies
+                    .push(Dependency { crate_id: cfg_if, name: CrateName::new("cfg_if").unwrap() });
+                true
+            }
+            _ => false,
+        }
+    }
+
+    fn hacky_find_crate(&self, display_name: &str) -> Option<CrateId> {
+        self.iter().find(|it| self[*it].display_name.as_deref() == Some(display_name))
+    }
 }
 
 impl ops::Index<CrateId> for CrateGraph {
diff --git a/crates/base_db/src/lib.rs b/crates/base_db/src/lib.rs
index e38aa7257..0804202d6 100644
--- a/crates/base_db/src/lib.rs
+++ b/crates/base_db/src/lib.rs
@@ -13,8 +13,8 @@ pub use crate::{
     cancellation::Canceled,
     change::Change,
     input::{
-        CrateData, CrateGraph, CrateId, CrateName, Dependency, Edition, Env, FileId, ProcMacroId,
-        SourceRoot, SourceRootId,
+        CrateData, CrateDisplayName, CrateGraph, CrateId, CrateName, Dependency, Edition, Env,
+        FileId, ProcMacroId, SourceRoot, SourceRootId,
     },
 };
 pub use salsa;
diff --git a/crates/call_info/Cargo.toml b/crates/call_info/Cargo.toml
new file mode 100644
index 000000000..98c0bd6db
--- /dev/null
+++ b/crates/call_info/Cargo.toml
@@ -0,0 +1,26 @@
+[package]
+name = "call_info"
+version = "0.0.0"
+description = "TBD"
+license = "MIT OR Apache-2.0"
+authors = ["rust-analyzer developers"]
+edition = "2018"
+
+[lib]
+doctest = false
+
+[dependencies]
+either = "1.5.3"
+
+stdx = { path = "../stdx", version = "0.0.0" }
+syntax = { path = "../syntax", version = "0.0.0" }
+base_db = { path = "../base_db", version = "0.0.0" }
+ide_db = { path = "../ide_db", version = "0.0.0" }
+test_utils = { path = "../test_utils", version = "0.0.0" }
+
+# call_info crate should depend only on the top-level `hir` package. if you need
+# something from some `hir_xxx` subpackage, reexport the API via `hir`.
+hir = { path = "../hir", version = "0.0.0" }
+
+[dev-dependencies]
+expect-test = "1.0"
diff --git a/crates/ide/src/call_info.rs b/crates/call_info/src/lib.rs
index d7b2b926e..c45406c25 100644
--- a/crates/ide/src/call_info.rs
+++ b/crates/call_info/src/lib.rs
@@ -1,4 +1,5 @@
-//! FIXME: write short doc here
+//! This crate provides primitives for tracking the information about a call site.
+use base_db::FilePosition;
 use either::Either;
 use hir::{HasAttrs, HirDisplay, Semantics, Type};
 use ide_db::RootDatabase;
@@ -9,8 +10,6 @@ use syntax::{
 };
 use test_utils::mark;
 
-use crate::FilePosition;
-
 /// Contains information about a call site. Specifically the
 /// `FunctionSignature`and current parameter.
 #[derive(Debug)]
@@ -40,7 +39,7 @@ impl CallInfo {
 }
 
 /// Computes parameter information for the given call expression.
-pub(crate) fn call_info(db: &RootDatabase, position: FilePosition) -> Option<CallInfo> {
+pub fn call_info(db: &RootDatabase, position: FilePosition) -> Option<CallInfo> {
     let sema = Semantics::new(db);
     let file = sema.parse(position.file_id);
     let file = file.syntax();
@@ -141,13 +140,13 @@ fn call_info_impl(
 }
 
 #[derive(Debug)]
-pub(crate) struct ActiveParameter {
-    pub(crate) ty: Type,
-    pub(crate) name: String,
+pub struct ActiveParameter {
+    pub ty: Type,
+    pub name: String,
 }
 
 impl ActiveParameter {
-    pub(crate) fn at(db: &RootDatabase, position: FilePosition) -> Option<Self> {
+    pub fn at(db: &RootDatabase, position: FilePosition) -> Option<Self> {
         let sema = Semantics::new(db);
         let file = sema.parse(position.file_id);
         let file = file.syntax();
@@ -156,7 +155,7 @@ impl ActiveParameter {
         Self::at_token(&sema, token)
     }
 
-    pub(crate) fn at_token(sema: &Semantics<RootDatabase>, token: SyntaxToken) -> Option<Self> {
+    pub fn at_token(sema: &Semantics<RootDatabase>, token: SyntaxToken) -> Option<Self> {
         let (signature, active_parameter) = call_info_impl(&sema, token)?;
 
         let idx = active_parameter?;
@@ -172,7 +171,7 @@ impl ActiveParameter {
 }
 
 #[derive(Debug)]
-pub(crate) enum FnCallNode {
+pub enum FnCallNode {
     CallExpr(ast::CallExpr),
     MethodCallExpr(ast::MethodCallExpr),
 }
@@ -196,7 +195,7 @@ impl FnCallNode {
         })
     }
 
-    pub(crate) fn with_node_exact(node: &SyntaxNode) -> Option<FnCallNode> {
+    pub fn with_node_exact(node: &SyntaxNode) -> Option<FnCallNode> {
         match_ast! {
             match node {
                 ast::CallExpr(it) => Some(FnCallNode::CallExpr(it)),
@@ -206,7 +205,7 @@ impl FnCallNode {
         }
     }
 
-    pub(crate) fn name_ref(&self) -> Option<ast::NameRef> {
+    pub fn name_ref(&self) -> Option<ast::NameRef> {
         match self {
             FnCallNode::CallExpr(call_expr) => Some(match call_expr.expr()? {
                 ast::Expr::PathExpr(path_expr) => path_expr.path()?.segment()?.name_ref()?,
@@ -229,14 +228,28 @@ impl FnCallNode {
 
 #[cfg(test)]
 mod tests {
+    use base_db::{fixture::ChangeFixture, FilePosition};
     use expect_test::{expect, Expect};
-    use test_utils::mark;
-
-    use crate::fixture;
+    use ide_db::RootDatabase;
+    use test_utils::{mark, RangeOrOffset};
+
+    /// Creates analysis from a multi-file fixture, returns positions marked with <|>.
+    pub(crate) fn position(ra_fixture: &str) -> (RootDatabase, FilePosition) {
+        let change_fixture = ChangeFixture::parse(ra_fixture);
+        let mut database = RootDatabase::default();
+        database.apply_change(change_fixture.change);
+        let (file_id, range_or_offset) =
+            change_fixture.file_position.expect("expected a marker (<|>)");
+        let offset = match range_or_offset {
+            RangeOrOffset::Range(_) => panic!(),
+            RangeOrOffset::Offset(it) => it,
+        };
+        (database, FilePosition { file_id, offset })
+    }
 
     fn check(ra_fixture: &str, expect: Expect) {
-        let (analysis, position) = fixture::position(ra_fixture);
-        let call_info = analysis.call_info(position).unwrap();
+        let (db, position) = position(ra_fixture);
+        let call_info = crate::call_info(&db, position);
         let actual = match call_info {
             Some(call_info) => {
                 let docs = match &call_info.doc {
diff --git a/crates/completion/Cargo.toml b/crates/completion/Cargo.toml
new file mode 100644
index 000000000..25192456a
--- /dev/null
+++ b/crates/completion/Cargo.toml
@@ -0,0 +1,32 @@
+[package]
+name = "completion"
+version = "0.0.0"
+description = "TBD"
+license = "MIT OR Apache-2.0"
+authors = ["rust-analyzer developers"]
+edition = "2018"
+
+[lib]
+doctest = false
+
+[dependencies]
+itertools = "0.9.0"
+log = "0.4.8"
+rustc-hash = "1.1.0"
+
+stdx = { path = "../stdx", version = "0.0.0" }
+syntax = { path = "../syntax", version = "0.0.0" }
+text_edit = { path = "../text_edit", version = "0.0.0" }
+base_db = { path = "../base_db", version = "0.0.0" }
+ide_db = { path = "../ide_db", version = "0.0.0" }
+profile = { path = "../profile", version = "0.0.0" }
+test_utils = { path = "../test_utils", version = "0.0.0" }
+assists = { path = "../assists", version = "0.0.0" }
+call_info = { path = "../call_info", version = "0.0.0" }
+
+# completions crate should depend only on the top-level `hir` package. if you need
+# something from some `hir_xxx` subpackage, reexport the API via `hir`.
+hir = { path = "../hir", version = "0.0.0" }
+
+[dev-dependencies]
+expect-test = "1.0"
diff --git a/crates/ide/src/completion/complete_attribute.rs b/crates/completion/src/complete_attribute.rs
index f4a9864d1..f97ab7dd0 100644
--- a/crates/ide/src/completion/complete_attribute.rs
+++ b/crates/completion/src/complete_attribute.rs
@@ -6,10 +6,10 @@
 use rustc_hash::FxHashSet;
 use syntax::{ast, AstNode, SyntaxKind};
 
-use crate::completion::{
+use crate::{
     completion_context::CompletionContext,
     completion_item::{CompletionItem, CompletionItemKind, CompletionKind, Completions},
-    generated_features::FEATURES,
+    generated_lint_completions::{CLIPPY_LINTS, FEATURES},
 };
 
 pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
@@ -23,14 +23,15 @@ pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext)
             complete_derive(acc, ctx, token_tree)
         }
         (Some(path), Some(token_tree)) if path.to_string() == "feature" => {
-            complete_lint(acc, ctx, token_tree, FEATURES)
+            complete_lint(acc, ctx, token_tree, FEATURES);
         }
         (Some(path), Some(token_tree))
             if ["allow", "warn", "deny", "forbid"]
                 .iter()
                 .any(|lint_level| lint_level == &path.to_string()) =>
         {
-            complete_lint(acc, ctx, token_tree, DEFAULT_LINT_COMPLETIONS)
+            complete_lint(acc, ctx, token_tree.clone(), DEFAULT_LINT_COMPLETIONS);
+            complete_lint(acc, ctx, token_tree, CLIPPY_LINTS);
         }
         (_, Some(_token_tree)) => {}
         _ => complete_attribute_start(acc, ctx, attribute),
@@ -389,7 +390,7 @@ const DEFAULT_LINT_COMPLETIONS: &[LintCompletion] = &[
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use crate::{test_utils::completion_list, CompletionKind};
 
     fn check(ra_fixture: &str, expect: Expect) {
         let actual = completion_list(ra_fixture, CompletionKind::Attribute);
@@ -418,130 +419,6 @@ struct Test {}
     }
 
     #[test]
-    fn empty_lint_completion() {
-        check(
-            r#"#[allow(<|>)]"#,
-            expect![[r#"
-                at absolute_paths_not_starting_with_crate fully qualified paths that start with a module name instead of `crate`, `self`, or an extern crate name
-                at ambiguous_associated_items ambiguous associated items
-                at anonymous_parameters detects anonymous parameters
-                at arithmetic_overflow arithmetic operation overflows
-                at array_into_iter  detects calling `into_iter` on arrays
-                at asm_sub_register using only a subset of a register for inline asm inputs
-                at bare_trait_objects suggest using `dyn Trait` for trait objects
-                at bindings_with_variant_name detects pattern bindings with the same name as one of the matched variants
-                at box_pointers     use of owned (Box type) heap memory
-                at cenum_impl_drop_cast a C-like enum implementing Drop is cast
-                at clashing_extern_declarations detects when an extern fn has been declared with the same name but different types
-                at coherence_leak_check distinct impls distinguished only by the leak-check code
-                at conflicting_repr_hints conflicts between `#[repr(..)]` hints that were previously accepted and used in practice
-                at confusable_idents detects visually confusable pairs between identifiers
-                at const_err        constant evaluation detected erroneous expression
-                at dead_code        detect unused, unexported items
-                at deprecated       detects use of deprecated items
-                at deprecated_in_future detects use of items that will be deprecated in a future version
-                at elided_lifetimes_in_paths hidden lifetime parameters in types are deprecated
-                at ellipsis_inclusive_range_patterns `...` range patterns are deprecated
-                at explicit_outlives_requirements outlives requirements can be inferred
-                at exported_private_dependencies public interface leaks type from a private dependency
-                at ill_formed_attribute_input ill-formed attribute inputs that were previously accepted and used in practice
-                at illegal_floating_point_literal_pattern floating-point literals cannot be used in patterns
-                at improper_ctypes  proper use of libc types in foreign modules
-                at improper_ctypes_definitions proper use of libc types in foreign item definitions
-                at incomplete_features incomplete features that may function improperly in some or all cases
-                at incomplete_include trailing content in included file
-                at indirect_structural_match pattern with const indirectly referencing non-structural-match type
-                at inline_no_sanitize detects incompatible use of `#[inline(always)]` and `#[no_sanitize(...)]`
-                at intra_doc_link_resolution_failure failures in resolving intra-doc link targets
-                at invalid_codeblock_attributes codeblock attribute looks a lot like a known one
-                at invalid_type_param_default type parameter default erroneously allowed in invalid location
-                at invalid_value    an invalid value is being created (such as a NULL reference)
-                at irrefutable_let_patterns detects irrefutable patterns in if-let and while-let statements
-                at keyword_idents   detects edition keywords being used as an identifier
-                at late_bound_lifetime_arguments detects generic lifetime arguments in path segments with late bound lifetime parameters
-                at macro_expanded_macro_exports_accessed_by_absolute_paths macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
-                at macro_use_extern_crate the `#[macro_use]` attribute is now deprecated in favor of using macros via the module system
-                at meta_variable_misuse possible meta-variable misuse at macro definition
-                at missing_copy_implementations detects potentially-forgotten implementations of `Copy`
-                at missing_crate_level_docs detects crates with no crate-level documentation
-                at missing_debug_implementations detects missing implementations of Debug
-                at missing_doc_code_examples detects publicly-exported items without code samples in their documentation
-                at missing_docs     detects missing documentation for public members
-                at missing_fragment_specifier detects missing fragment specifiers in unused `macro_rules!` patterns
-                at mixed_script_confusables detects Unicode scripts whose mixed script confusables codepoints are solely used
-                at mutable_borrow_reservation_conflict reservation of a two-phased borrow conflicts with other shared borrows
-                at mutable_transmutes mutating transmuted &mut T from &T may cause undefined behavior
-                at no_mangle_const_items const items will not have their symbols exported
-                at no_mangle_generic_items generic items must be mangled
-                at non_ascii_idents detects non-ASCII identifiers
-                at non_camel_case_types types, variants, traits and type parameters should have camel case names
-                at non_shorthand_field_patterns using `Struct { x: x }` instead of `Struct { x }` in a pattern
-                at non_snake_case   variables, methods, functions, lifetime parameters and modules should have snake case names
-                at non_upper_case_globals static constants should have uppercase identifiers
-                at order_dependent_trait_objects trait-object types were treated as different depending on marker-trait order
-                at overflowing_literals literal out of range for its type
-                at overlapping_patterns detects overlapping patterns
-                at path_statements  path statements with no effect
-                at patterns_in_fns_without_body patterns in functions without body were erroneously allowed
-                at private_doc_tests detects code samples in docs of private items not documented by rustdoc
-                at private_in_public detect private items in public interfaces not caught by the old implementation
-                at proc_macro_derive_resolution_fallback detects proc macro derives using inaccessible names from parent modules
-                at pub_use_of_private_extern_crate detect public re-exports of private extern crates
-                at redundant_semicolons detects unnecessary trailing semicolons
-                at renamed_and_removed_lints lints that have been renamed or removed
-                at safe_packed_borrows safe borrows of fields of packed structs were erroneously allowed
-                at single_use_lifetimes detects lifetime parameters that are only used once
-                at soft_unstable    a feature gate that doesn't break dependent crates
-                at stable_features  stable features found in `#[feature]` directive
-                at trivial_bounds   these bounds don't depend on an type parameters
-                at trivial_casts    detects trivial casts which could be removed
-                at trivial_numeric_casts detects trivial casts of numeric types which could be removed
-                at type_alias_bounds bounds in type aliases are not enforced
-                at tyvar_behind_raw_pointer raw pointer to an inference variable
-                at unaligned_references detects unaligned references to fields of packed structs
-                at uncommon_codepoints detects uncommon Unicode codepoints in identifiers
-                at unconditional_panic operation will cause a panic at runtime
-                at unconditional_recursion functions that cannot return without calling themselves
-                at unknown_crate_types unknown crate type found in `#[crate_type]` directive
-                at unknown_lints    unrecognized lint attribute
-                at unnameable_test_items detects an item that cannot be named being marked as `#[test_case]`
-                at unreachable_code detects unreachable code paths
-                at unreachable_patterns detects unreachable patterns
-                at unreachable_pub  `pub` items not reachable from crate root
-                at unsafe_code      usage of `unsafe` code
-                at unsafe_op_in_unsafe_fn unsafe operations in unsafe functions without an explicit unsafe block are deprecated
-                at unstable_features enabling unstable features (deprecated. do not use)
-                at unstable_name_collisions detects name collision with an existing but unstable method
-                at unused_allocation detects unnecessary allocations that can be eliminated
-                at unused_assignments detect assignments that will never be read
-                at unused_attributes detects attributes that were not used by the compiler
-                at unused_braces    unnecessary braces around an expression
-                at unused_comparisons comparisons made useless by limits of the types involved
-                at unused_crate_dependencies crate dependencies that are never used
-                at unused_doc_comments detects doc comments that aren't used by rustdoc
-                at unused_extern_crates extern crates that are never used
-                at unused_features  unused features found in crate-level `#[feature]` directives
-                at unused_import_braces unnecessary braces around an imported item
-                at unused_imports   imports that are never used
-                at unused_labels    detects labels that are never used
-                at unused_lifetimes detects lifetime parameters that are never used
-                at unused_macros    detects macros that were not used
-                at unused_must_use  unused result of a type flagged as `#[must_use]`
-                at unused_mut       detect mut variables which don't need to be mutable
-                at unused_parens    `if`, `match`, `while` and `return` do not need parentheses
-                at unused_qualifications detects unnecessarily qualified names
-                at unused_results   unused result of an expression in a statement
-                at unused_unsafe    unnecessary use of an `unsafe` block
-                at unused_variables detect variables which are not used in any way
-                at variant_size_differences detects enums with widely varying variant sizes
-                at warnings         mass-change the level for lints which produce warnings
-                at where_clauses_object_safety checks the object safety of where clauses
-                at while_true       suggest using `loop { }` instead of `while true { }`
-        "#]],
-        )
-    }
-
-    #[test]
     fn no_completion_for_incorrect_derive() {
         check(
             r#"
diff --git a/crates/ide/src/completion/complete_dot.rs b/crates/completion/src/complete_dot.rs
index 0b9f1798a..0eabb48ae 100644
--- a/crates/ide/src/completion/complete_dot.rs
+++ b/crates/completion/src/complete_dot.rs
@@ -4,7 +4,7 @@ use hir::{HasVisibility, Type};
 use rustc_hash::FxHashSet;
 use test_utils::mark;
 
-use crate::completion::{completion_context::CompletionContext, completion_item::Completions};
+use crate::{completion_context::CompletionContext, completion_item::Completions};
 
 /// Complete dot accesses, i.e. fields or methods.
 pub(super) fn complete_dot(acc: &mut Completions, ctx: &CompletionContext) {
@@ -64,7 +64,7 @@ mod tests {
     use expect_test::{expect, Expect};
     use test_utils::mark;
 
-    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use crate::{test_utils::completion_list, CompletionKind};
 
     fn check(ra_fixture: &str, expect: Expect) {
         let actual = completion_list(ra_fixture, CompletionKind::Reference);
@@ -413,4 +413,19 @@ fn foo() {
             "#]],
         );
     }
+
+    #[test]
+    fn completes_method_call_when_receiver_is_a_macro_call() {
+        check(
+            r#"
+struct S;
+impl S { fn foo(&self) {} }
+macro_rules! make_s { () => { S }; }
+fn main() { make_s!().f<|>; }
+"#,
+            expect![[r#"
+                me foo() fn foo(&self)
+            "#]],
+        )
+    }
 }
diff --git a/crates/ide/src/completion/complete_fn_param.rs b/crates/completion/src/complete_fn_param.rs
index 9efe25461..918996727 100644
--- a/crates/ide/src/completion/complete_fn_param.rs
+++ b/crates/completion/src/complete_fn_param.rs
@@ -6,7 +6,7 @@ use syntax::{
     match_ast, AstNode,
 };
 
-use crate::completion::{CompletionContext, CompletionItem, CompletionKind, Completions};
+use crate::{CompletionContext, CompletionItem, CompletionKind, Completions};
 
 /// Complete repeated parameters, both name and type. For example, if all
 /// functions in a file have a `spam: &mut Spam` parameter, a completion with
@@ -68,7 +68,7 @@ pub(super) fn complete_fn_param(acc: &mut Completions, ctx: &CompletionContext)
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use crate::{test_utils::completion_list, CompletionKind};
 
     fn check(ra_fixture: &str, expect: Expect) {
         let actual = completion_list(ra_fixture, CompletionKind::Magic);
diff --git a/crates/ide/src/completion/complete_keyword.rs b/crates/completion/src/complete_keyword.rs
index e59747095..ace914f3f 100644
--- a/crates/ide/src/completion/complete_keyword.rs
+++ b/crates/completion/src/complete_keyword.rs
@@ -1,11 +1,9 @@
-//! FIXME: write short doc here
+//! Completes keywords.
 
 use syntax::{ast, SyntaxKind};
 use test_utils::mark;
 
-use crate::completion::{
-    CompletionContext, CompletionItem, CompletionItemKind, CompletionKind, Completions,
-};
+use crate::{CompletionContext, CompletionItem, CompletionItemKind, CompletionKind, Completions};
 
 pub(super) fn complete_use_tree_keyword(acc: &mut Completions, ctx: &CompletionContext) {
     // complete keyword "crate" in use stmt
@@ -177,7 +175,7 @@ fn complete_return(
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{
+    use crate::{
         test_utils::{check_edit, completion_list},
         CompletionKind,
     };
diff --git a/crates/ide/src/completion/complete_macro_in_item_position.rs b/crates/completion/src/complete_macro_in_item_position.rs
index fc8625d8e..d1d8c23d2 100644
--- a/crates/ide/src/completion/complete_macro_in_item_position.rs
+++ b/crates/completion/src/complete_macro_in_item_position.rs
@@ -1,6 +1,6 @@
-//! FIXME: write short doc here
+//! Completes macro invocations used in item position.
 
-use crate::completion::{CompletionContext, Completions};
+use crate::{CompletionContext, Completions};
 
 pub(super) fn complete_macro_in_item_position(acc: &mut Completions, ctx: &CompletionContext) {
     // Show only macros in top level.
@@ -17,7 +17,7 @@ pub(super) fn complete_macro_in_item_position(acc: &mut Completions, ctx: &Compl
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use crate::{test_utils::completion_list, CompletionKind};
 
     fn check(ra_fixture: &str, expect: Expect) {
         let actual = completion_list(ra_fixture, CompletionKind::Reference);
diff --git a/crates/ide/src/completion/complete_mod.rs b/crates/completion/src/complete_mod.rs
index c7a99bdc3..35a57aba3 100644
--- a/crates/ide/src/completion/complete_mod.rs
+++ b/crates/completion/src/complete_mod.rs
@@ -150,7 +150,7 @@ fn module_chain_to_containing_module_file(
 
 #[cfg(test)]
 mod tests {
-    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use crate::{test_utils::completion_list, CompletionKind};
     use expect_test::{expect, Expect};
 
     fn check(ra_fixture: &str, expect: Expect) {
diff --git a/crates/ide/src/completion/complete_pattern.rs b/crates/completion/src/complete_pattern.rs
index 5a13574d4..5606dcdd9 100644
--- a/crates/ide/src/completion/complete_pattern.rs
+++ b/crates/completion/src/complete_pattern.rs
@@ -1,6 +1,6 @@
-//! FIXME: write short doc here
+//! Completes constats and paths in patterns.
 
-use crate::completion::{CompletionContext, Completions};
+use crate::{CompletionContext, Completions};
 
 /// Completes constats and paths in patterns.
 pub(super) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
@@ -35,7 +35,7 @@ pub(super) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use crate::{test_utils::completion_list, CompletionKind};
 
     fn check(ra_fixture: &str, expect: Expect) {
         let actual = completion_list(ra_fixture, CompletionKind::Reference);
diff --git a/crates/ide/src/completion/complete_postfix.rs b/crates/completion/src/complete_postfix.rs
index db5319618..700573cf2 100644
--- a/crates/ide/src/completion/complete_postfix.rs
+++ b/crates/completion/src/complete_postfix.rs
@@ -1,4 +1,4 @@
-//! FIXME: write short doc here
+//! Postfix completions, like `Ok(10).ifl<|>` => `if let Ok() = Ok(10) { <|> }`.
 
 mod format_like;
 
@@ -11,11 +11,9 @@ use text_edit::TextEdit;
 
 use self::format_like::add_format_like_completions;
 use crate::{
-    completion::{
-        completion_config::SnippetCap,
-        completion_context::CompletionContext,
-        completion_item::{Builder, CompletionKind, Completions},
-    },
+    completion_config::SnippetCap,
+    completion_context::CompletionContext,
+    completion_item::{Builder, CompletionKind, Completions},
     CompletionItem, CompletionItemKind,
 };
 
@@ -263,7 +261,7 @@ fn postfix_snippet(
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{
+    use crate::{
         test_utils::{check_edit, completion_list},
         CompletionKind,
     };
diff --git a/crates/ide/src/completion/complete_postfix/format_like.rs b/crates/completion/src/complete_postfix/format_like.rs
index 50d1e5c81..205c384e2 100644
--- a/crates/ide/src/completion/complete_postfix/format_like.rs
+++ b/crates/completion/src/complete_postfix/format_like.rs
@@ -14,7 +14,7 @@
 //   + `logw` -> `log::warn!(...)`
 //   + `loge` -> `log::error!(...)`
 
-use crate::completion::{
+use crate::{
     complete_postfix::postfix_snippet, completion_config::SnippetCap,
     completion_context::CompletionContext, completion_item::Completions,
 };
diff --git a/crates/ide/src/completion/complete_qualified_path.rs b/crates/completion/src/complete_qualified_path.rs
index 2fafedd47..80b271fdf 100644
--- a/crates/ide/src/completion/complete_qualified_path.rs
+++ b/crates/completion/src/complete_qualified_path.rs
@@ -5,7 +5,7 @@ use rustc_hash::FxHashSet;
 use syntax::AstNode;
 use test_utils::mark;
 
-use crate::completion::{CompletionContext, Completions};
+use crate::{CompletionContext, Completions};
 
 pub(super) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionContext) {
     let path = match &ctx.path_qual {
@@ -149,7 +149,7 @@ mod tests {
     use expect_test::{expect, Expect};
     use test_utils::mark;
 
-    use crate::completion::{
+    use crate::{
         test_utils::{check_edit, completion_list},
         CompletionKind,
     };
diff --git a/crates/ide/src/completion/complete_record.rs b/crates/completion/src/complete_record.rs
index ceb8d16c1..129ddc055 100644
--- a/crates/ide/src/completion/complete_record.rs
+++ b/crates/completion/src/complete_record.rs
@@ -1,5 +1,5 @@
 //! Complete fields in record literals and patterns.
-use crate::completion::{CompletionContext, Completions};
+use crate::{CompletionContext, Completions};
 
 pub(super) fn complete_record(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
     let missing_fields = match (ctx.record_pat_syntax.as_ref(), ctx.record_lit_syntax.as_ref()) {
@@ -20,7 +20,7 @@ pub(super) fn complete_record(acc: &mut Completions, ctx: &CompletionContext) ->
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use crate::{test_utils::completion_list, CompletionKind};
 
     fn check(ra_fixture: &str, expect: Expect) {
         let actual = completion_list(ra_fixture, CompletionKind::Reference);
diff --git a/crates/ide/src/completion/complete_snippet.rs b/crates/completion/src/complete_snippet.rs
index 4837d2910..06096722b 100644
--- a/crates/ide/src/completion/complete_snippet.rs
+++ b/crates/completion/src/complete_snippet.rs
@@ -1,6 +1,6 @@
-//! FIXME: write short doc here
+//! This file provides snippet completions, like `pd` => `eprintln!(...)`.
 
-use crate::completion::{
+use crate::{
     completion_config::SnippetCap, completion_item::Builder, CompletionContext, CompletionItem,
     CompletionItemKind, CompletionKind, Completions,
 };
@@ -71,7 +71,7 @@ fn ${1:feature}() {
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{test_utils::completion_list, CompletionKind};
+    use crate::{test_utils::completion_list, CompletionKind};
 
     fn check(ra_fixture: &str, expect: Expect) {
         let actual = completion_list(ra_fixture, CompletionKind::Snippet);
diff --git a/crates/ide/src/completion/complete_trait_impl.rs b/crates/completion/src/complete_trait_impl.rs
index ff115df92..c06af99e2 100644
--- a/crates/ide/src/completion/complete_trait_impl.rs
+++ b/crates/completion/src/complete_trait_impl.rs
@@ -35,15 +35,18 @@ use assists::utils::get_missing_assoc_items;
 use hir::{self, HasAttrs, HasSource};
 use syntax::{
     ast::{self, edit, Impl},
+    display::function_declaration,
     AstNode, SyntaxKind, SyntaxNode, TextRange, T,
 };
 use text_edit::TextEdit;
 
 use crate::{
-    completion::{
-        CompletionContext, CompletionItem, CompletionItemKind, CompletionKind, Completions,
-    },
-    display::function_declaration,
+    CompletionContext,
+    CompletionItem,
+    CompletionItemKind,
+    CompletionKind,
+    Completions,
+    // display::function_declaration,
 };
 
 #[derive(Debug, PartialEq, Eq)]
@@ -237,7 +240,7 @@ fn make_const_compl_syntax(const_: &ast::Const) -> String {
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::completion::{
+    use crate::{
         test_utils::{check_edit, completion_list},
         CompletionKind,
     };
diff --git a/crates/ide/src/completion/complete_unqualified_path.rs b/crates/completion/src/complete_unqualified_path.rs
index 8b6757195..5464a160d 100644
--- a/crates/ide/src/completion/complete_unqualified_path.rs
+++ b/crates/completion/src/complete_unqualified_path.rs
@@ -4,7 +4,7 @@ use hir::{Adt, ModuleDef, ScopeDef, Type};
 use syntax::AstNode;
 use test_utils::mark;
 
-use crate::completion::{CompletionContext, Completions};
+use crate::{CompletionContext, Completions};
 
 pub(super) fn complete_unqualified_path(acc: &mut Completions, ctx: &CompletionContext) {
     if !(ctx.is_trivial_path || ctx.is_pat_binding_or_const) {
@@ -68,7 +68,7 @@ mod tests {
     use expect_test::{expect, Expect};
     use test_utils::mark;
 
-    use crate::completion::{
+    use crate::{
         test_utils::{check_edit, completion_list},
         CompletionKind,
     };
diff --git a/crates/ide/src/completion/completion_config.rs b/crates/completion/src/completion_config.rs
index 71b49ace8..71b49ace8 100644
--- a/crates/ide/src/completion/completion_config.rs
+++ b/crates/completion/src/completion_config.rs
diff --git a/crates/ide/src/completion/completion_context.rs b/crates/completion/src/completion_context.rs
index 8dea8a4bf..dc4e136c6 100644
--- a/crates/ide/src/completion/completion_context.rs
+++ b/crates/completion/src/completion_context.rs
@@ -1,6 +1,7 @@
-//! FIXME: write short doc here
+//! See `CompletionContext` structure.
 
-use base_db::SourceDatabase;
+use base_db::{FilePosition, SourceDatabase};
+use call_info::ActiveParameter;
 use hir::{Local, ScopeDef, Semantics, SemanticsScope, Type};
 use ide_db::RootDatabase;
 use syntax::{
@@ -13,17 +14,14 @@ use test_utils::mark;
 use text_edit::Indel;
 
 use crate::{
-    call_info::ActiveParameter,
-    completion::{
-        patterns::{
-            has_bind_pat_parent, has_block_expr_parent, has_field_list_parent,
-            has_impl_as_prev_sibling, has_impl_parent, has_item_list_or_source_file_parent,
-            has_ref_parent, has_trait_as_prev_sibling, has_trait_parent, if_is_prev,
-            is_in_loop_body, is_match_arm, unsafe_is_prev,
-        },
-        CompletionConfig,
+    patterns::{
+        fn_is_prev, for_is_prev2, has_bind_pat_parent, has_block_expr_parent,
+        has_field_list_parent, has_impl_as_prev_sibling, has_impl_parent,
+        has_item_list_or_source_file_parent, has_ref_parent, has_trait_as_prev_sibling,
+        has_trait_parent, if_is_prev, inside_impl_trait_block, is_in_loop_body, is_match_arm,
+        unsafe_is_prev,
     },
-    FilePosition,
+    CompletionConfig,
 };
 
 /// `CompletionContext` is created early during completion to figure out, where
@@ -86,11 +84,14 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) in_loop_body: bool,
     pub(super) has_trait_parent: bool,
     pub(super) has_impl_parent: bool,
+    pub(super) inside_impl_trait_block: bool,
     pub(super) has_field_list_parent: bool,
     pub(super) trait_as_prev_sibling: bool,
     pub(super) impl_as_prev_sibling: bool,
     pub(super) is_match_arm: bool,
     pub(super) has_item_list_or_source_file_parent: bool,
+    pub(super) for_is_prev2: bool,
+    pub(super) fn_is_prev: bool,
     pub(super) locals: Vec<(String, Local)>,
 }
 
@@ -168,12 +169,15 @@ impl<'a> CompletionContext<'a> {
             block_expr_parent: false,
             has_trait_parent: false,
             has_impl_parent: false,
+            inside_impl_trait_block: false,
             has_field_list_parent: false,
             trait_as_prev_sibling: false,
             impl_as_prev_sibling: false,
             if_is_prev: false,
             is_match_arm: false,
             has_item_list_or_source_file_parent: false,
+            for_is_prev2: false,
+            fn_is_prev: false,
             locals,
         };
 
@@ -221,6 +225,15 @@ impl<'a> CompletionContext<'a> {
         Some(ctx)
     }
 
+    /// Checks whether completions in that particular case don't make much sense.
+    /// Examples:
+    /// - `fn <|>` -- we expect function name, it's unlikely that "hint" will be helpful.
+    ///   Exception for this case is `impl Trait for Foo`, where we would like to hint trait method names.
+    /// - `for _ i<|>` -- obviously, it'll be "in" keyword.
+    pub(crate) fn no_completion_required(&self) -> bool {
+        (self.fn_is_prev && !self.inside_impl_trait_block) || self.for_is_prev2
+    }
+
     /// The range of the identifier that is being completed.
     pub(crate) fn source_range(&self) -> TextRange {
         // check kind of macro-expanded token, but use range of original token
@@ -244,6 +257,7 @@ impl<'a> CompletionContext<'a> {
         self.in_loop_body = is_in_loop_body(syntax_element.clone());
         self.has_trait_parent = has_trait_parent(syntax_element.clone());
         self.has_impl_parent = has_impl_parent(syntax_element.clone());
+        self.inside_impl_trait_block = inside_impl_trait_block(syntax_element.clone());
         self.has_field_list_parent = has_field_list_parent(syntax_element.clone());
         self.impl_as_prev_sibling = has_impl_as_prev_sibling(syntax_element.clone());
         self.trait_as_prev_sibling = has_trait_as_prev_sibling(syntax_element.clone());
@@ -253,6 +267,8 @@ impl<'a> CompletionContext<'a> {
         self.mod_declaration_under_caret =
             find_node_at_offset::<ast::Module>(&file_with_fake_ident, offset)
                 .filter(|module| module.item_list().is_none());
+        self.for_is_prev2 = for_is_prev2(syntax_element.clone());
+        self.fn_is_prev = fn_is_prev(syntax_element.clone());
     }
 
     fn fill(
diff --git a/crates/ide/src/completion/completion_item.rs b/crates/completion/src/completion_item.rs
index 9377cdc57..f8be0ad2b 100644
--- a/crates/ide/src/completion/completion_item.rs
+++ b/crates/completion/src/completion_item.rs
@@ -1,4 +1,4 @@
-//! FIXME: write short doc here
+//! See `CompletionItem` structure.
 
 use std::fmt;
 
@@ -6,7 +6,7 @@ use hir::Documentation;
 use syntax::TextRange;
 use text_edit::TextEdit;
 
-use crate::completion::completion_config::SnippetCap;
+use crate::completion_config::SnippetCap;
 
 /// `CompletionItem` describes a single completion variant in the editor pop-up.
 /// It is basically a POD with various properties. To construct a
@@ -360,15 +360,15 @@ impl<'a> Into<CompletionItem> for Builder {
 
 /// Represents an in-progress set of completions being built.
 #[derive(Debug, Default)]
-pub(crate) struct Completions {
+pub struct Completions {
     buf: Vec<CompletionItem>,
 }
 
 impl Completions {
-    pub(crate) fn add(&mut self, item: impl Into<CompletionItem>) {
+    pub fn add(&mut self, item: impl Into<CompletionItem>) {
         self.buf.push(item.into())
     }
-    pub(crate) fn add_all<I>(&mut self, items: I)
+    pub fn add_all<I>(&mut self, items: I)
     where
         I: IntoIterator,
         I::Item: Into<CompletionItem>,
diff --git a/crates/completion/src/generated_lint_completions.rs b/crates/completion/src/generated_lint_completions.rs
new file mode 100644
index 000000000..5a7dba1f5
--- /dev/null
+++ b/crates/completion/src/generated_lint_completions.rs
@@ -0,0 +1,5 @@
+//! Generated file, do not edit by hand, see `xtask/src/codegen`
+
+use crate::complete_attribute::LintCompletion;
+pub (super) const FEATURES : & [LintCompletion] = & [LintCompletion { label : "link_args" , description : "# `link_args`\n\nThe tracking issue for this feature is: [#29596]\n\n[#29596]: https://github.com/rust-lang/rust/issues/29596\n\n------------------------\n\nYou can tell `rustc` how to customize linking, and that is via the `link_args`\nattribute. This attribute is applied to `extern` blocks and specifies raw flags\nwhich need to get passed to the linker when producing an artifact. An example\nusage would be:\n\n```rust,no_run\n#![feature(link_args)]\n\n#[link_args = \"-foo -bar -baz\"]\nextern {}\n# fn main() {}\n```\n\nNote that this feature is currently hidden behind the `feature(link_args)` gate\nbecause this is not a sanctioned way of performing linking. Right now `rustc`\nshells out to the system linker (`gcc` on most systems, `link.exe` on MSVC), so\nit makes sense to provide extra command line arguments, but this will not\nalways be the case. In the future `rustc` may use LLVM directly to link native\nlibraries, in which case `link_args` will have no meaning. You can achieve the\nsame effect as the `link_args` attribute with the `-C link-args` argument to\n`rustc`.\n\nIt is highly recommended to *not* use this attribute, and rather use the more\nformal `#[link(...)]` attribute on `extern` blocks instead.\n" } , LintCompletion { label : "repr128" , description : "# `repr128`\n\nThe tracking issue for this feature is: [#56071]\n\n[#56071]: https://github.com/rust-lang/rust/issues/56071\n\n------------------------\n\nThe `repr128` feature adds support for `#[repr(u128)]` on `enum`s.\n\n```rust\n#![feature(repr128)]\n\n#[repr(u128)]\nenum Foo {\n    Bar(u64),\n}\n```\n" } , LintCompletion { label : "crate_visibility_modifier" , description : "# `crate_visibility_modifier`\n\nThe tracking issue for this feature is: [#53120]\n\n[#53120]: https://github.com/rust-lang/rust/issues/53120\n\n-----\n\nThe `crate_visibility_modifier` feature allows the `crate` keyword to be used\nas a visibility modifier synonymous to `pub(crate)`, indicating that a type\n(function, _&c._) is to be visible to the entire enclosing crate, but not to\nother crates.\n\n```rust\n#![feature(crate_visibility_modifier)]\n\ncrate struct Foo {\n    bar: usize,\n}\n```\n" } , LintCompletion { label : "doc_masked" , description : "# `doc_masked`\n\nThe tracking issue for this feature is: [#44027]\n\n-----\n\nThe `doc_masked` feature allows a crate to exclude types from a given crate from appearing in lists\nof trait implementations. The specifics of the feature are as follows:\n\n1. When rustdoc encounters an `extern crate` statement annotated with a `#[doc(masked)]` attribute,\n   it marks the crate as being masked.\n\n2. When listing traits a given type implements, rustdoc ensures that traits from masked crates are\n   not emitted into the documentation.\n\n3. When listing types that implement a given trait, rustdoc ensures that types from masked crates\n   are not emitted into the documentation.\n\nThis feature was introduced in PR [#44026] to ensure that compiler-internal and\nimplementation-specific types and traits were not included in the standard library's documentation.\nSuch types would introduce broken links into the documentation.\n\n[#44026]: https://github.com/rust-lang/rust/pull/44026\n[#44027]: https://github.com/rust-lang/rust/pull/44027\n" } , LintCompletion { label : "cfg_sanitize" , description : "# `cfg_sanitize`\n\nThe tracking issue for this feature is: [#39699]\n\n[#39699]: https://github.com/rust-lang/rust/issues/39699\n\n------------------------\n\nThe `cfg_sanitize` feature makes it possible to execute different code\ndepending on whether a particular sanitizer is enabled or not.\n\n## Examples\n\n```rust\n#![feature(cfg_sanitize)]\n\n#[cfg(sanitize = \"thread\")]\nfn a() {\n    // ...\n}\n\n#[cfg(not(sanitize = \"thread\"))]\nfn a() {\n    // ...\n}\n\nfn b() {\n    if cfg!(sanitize = \"leak\") {\n        // ...\n    } else {\n        // ...\n    }\n}\n```\n" } , LintCompletion { label : "generators" , description : "# `generators`\n\nThe tracking issue for this feature is: [#43122]\n\n[#43122]: https://github.com/rust-lang/rust/issues/43122\n\n------------------------\n\nThe `generators` feature gate in Rust allows you to define generator or\ncoroutine literals. A generator is a \"resumable function\" that syntactically\nresembles a closure but compiles to much different semantics in the compiler\nitself. The primary feature of a generator is that it can be suspended during\nexecution to be resumed at a later date. Generators use the `yield` keyword to\n\"return\", and then the caller can `resume` a generator to resume execution just\nafter the `yield` keyword.\n\nGenerators are an extra-unstable feature in the compiler right now. Added in\n[RFC 2033] they're mostly intended right now as a information/constraint\ngathering phase. The intent is that experimentation can happen on the nightly\ncompiler before actual stabilization. A further RFC will be required to\nstabilize generators/coroutines and will likely contain at least a few small\ntweaks to the overall design.\n\n[RFC 2033]: https://github.com/rust-lang/rfcs/pull/2033\n\nA syntactical example of a generator is:\n\n```rust\n#![feature(generators, generator_trait)]\n\nuse std::ops::{Generator, GeneratorState};\nuse std::pin::Pin;\n\nfn main() {\n    let mut generator = || {\n        yield 1;\n        return \"foo\"\n    };\n\n    match Pin::new(&mut generator).resume(()) {\n        GeneratorState::Yielded(1) => {}\n        _ => panic!(\"unexpected value from resume\"),\n    }\n    match Pin::new(&mut generator).resume(()) {\n        GeneratorState::Complete(\"foo\") => {}\n        _ => panic!(\"unexpected value from resume\"),\n    }\n}\n```\n\nGenerators are closure-like literals which can contain a `yield` statement. The\n`yield` statement takes an optional expression of a value to yield out of the\ngenerator. All generator literals implement the `Generator` trait in the\n`std::ops` module. The `Generator` trait has one main method, `resume`, which\nresumes execution of the generator at the previous suspension point.\n\nAn example of the control flow of generators is that the following example\nprints all numbers in order:\n\n```rust\n#![feature(generators, generator_trait)]\n\nuse std::ops::Generator;\nuse std::pin::Pin;\n\nfn main() {\n    let mut generator = || {\n        println!(\"2\");\n        yield;\n        println!(\"4\");\n    };\n\n    println!(\"1\");\n    Pin::new(&mut generator).resume(());\n    println!(\"3\");\n    Pin::new(&mut generator).resume(());\n    println!(\"5\");\n}\n```\n\nAt this time the main intended use case of generators is an implementation\nprimitive for async/await syntax, but generators will likely be extended to\nergonomic implementations of iterators and other primitives in the future.\nFeedback on the design and usage is always appreciated!\n\n### The `Generator` trait\n\nThe `Generator` trait in `std::ops` currently looks like:\n\n```rust\n# #![feature(arbitrary_self_types, generator_trait)]\n# use std::ops::GeneratorState;\n# use std::pin::Pin;\n\npub trait Generator<R = ()> {\n    type Yield;\n    type Return;\n    fn resume(self: Pin<&mut Self>, resume: R) -> GeneratorState<Self::Yield, Self::Return>;\n}\n```\n\nThe `Generator::Yield` type is the type of values that can be yielded with the\n`yield` statement. The `Generator::Return` type is the returned type of the\ngenerator. This is typically the last expression in a generator's definition or\nany value passed to `return` in a generator. The `resume` function is the entry\npoint for executing the `Generator` itself.\n\nThe return value of `resume`, `GeneratorState`, looks like:\n\n```rust\npub enum GeneratorState<Y, R> {\n    Yielded(Y),\n    Complete(R),\n}\n```\n\nThe `Yielded` variant indicates that the generator can later be resumed. This\ncorresponds to a `yield` point in a generator. The `Complete` variant indicates\nthat the generator is complete and cannot be resumed again. Calling `resume`\nafter a generator has returned `Complete` will likely result in a panic of the\nprogram.\n\n### Closure-like semantics\n\nThe closure-like syntax for generators alludes to the fact that they also have\nclosure-like semantics. Namely:\n\n* When created, a generator executes no code. A closure literal does not\n  actually execute any of the closure's code on construction, and similarly a\n  generator literal does not execute any code inside the generator when\n  constructed.\n\n* Generators can capture outer variables by reference or by move, and this can\n  be tweaked with the `move` keyword at the beginning of the closure. Like\n  closures all generators will have an implicit environment which is inferred by\n  the compiler. Outer variables can be moved into a generator for use as the\n  generator progresses.\n\n* Generator literals produce a value with a unique type which implements the\n  `std::ops::Generator` trait. This allows actual execution of the generator\n  through the `Generator::resume` method as well as also naming it in return\n  types and such.\n\n* Traits like `Send` and `Sync` are automatically implemented for a `Generator`\n  depending on the captured variables of the environment. Unlike closures,\n  generators also depend on variables live across suspension points. This means\n  that although the ambient environment may be `Send` or `Sync`, the generator\n  itself may not be due to internal variables live across `yield` points being\n  not-`Send` or not-`Sync`. Note that generators do\n  not implement traits like `Copy` or `Clone` automatically.\n\n* Whenever a generator is dropped it will drop all captured environment\n  variables.\n\n### Generators as state machines\n\nIn the compiler, generators are currently compiled as state machines. Each\n`yield` expression will correspond to a different state that stores all live\nvariables over that suspension point. Resumption of a generator will dispatch on\nthe current state and then execute internally until a `yield` is reached, at\nwhich point all state is saved off in the generator and a value is returned.\n\nLet's take a look at an example to see what's going on here:\n\n```rust\n#![feature(generators, generator_trait)]\n\nuse std::ops::Generator;\nuse std::pin::Pin;\n\nfn main() {\n    let ret = \"foo\";\n    let mut generator = move || {\n        yield 1;\n        return ret\n    };\n\n    Pin::new(&mut generator).resume(());\n    Pin::new(&mut generator).resume(());\n}\n```\n\nThis generator literal will compile down to something similar to:\n\n```rust\n#![feature(arbitrary_self_types, generators, generator_trait)]\n\nuse std::ops::{Generator, GeneratorState};\nuse std::pin::Pin;\n\nfn main() {\n    let ret = \"foo\";\n    let mut generator = {\n        enum __Generator {\n            Start(&'static str),\n            Yield1(&'static str),\n            Done,\n        }\n\n        impl Generator for __Generator {\n            type Yield = i32;\n            type Return = &'static str;\n\n            fn resume(mut self: Pin<&mut Self>, resume: ()) -> GeneratorState<i32, &'static str> {\n                use std::mem;\n                match mem::replace(&mut *self, __Generator::Done) {\n                    __Generator::Start(s) => {\n                        *self = __Generator::Yield1(s);\n                        GeneratorState::Yielded(1)\n                    }\n\n                    __Generator::Yield1(s) => {\n                        *self = __Generator::Done;\n                        GeneratorState::Complete(s)\n                    }\n\n                    __Generator::Done => {\n                        panic!(\"generator resumed after completion\")\n                    }\n                }\n            }\n        }\n\n        __Generator::Start(ret)\n    };\n\n    Pin::new(&mut generator).resume(());\n    Pin::new(&mut generator).resume(());\n}\n```\n\nNotably here we can see that the compiler is generating a fresh type,\n`__Generator` in this case. This type has a number of states (represented here\nas an `enum`) corresponding to each of the conceptual states of the generator.\nAt the beginning we're closing over our outer variable `foo` and then that\nvariable is also live over the `yield` point, so it's stored in both states.\n\nWhen the generator starts it'll immediately yield 1, but it saves off its state\njust before it does so indicating that it has reached the yield point. Upon\nresuming again we'll execute the `return ret` which returns the `Complete`\nstate.\n\nHere we can also note that the `Done` state, if resumed, panics immediately as\nit's invalid to resume a completed generator. It's also worth noting that this\nis just a rough desugaring, not a normative specification for what the compiler\ndoes.\n" } , LintCompletion { label : "abi_ptx" , description : "# `abi_ptx`\n\nThe tracking issue for this feature is: [#38788]\n\n[#38788]: https://github.com/rust-lang/rust/issues/38788\n\n------------------------\n\nWhen emitting PTX code, all vanilla Rust functions (`fn`) get translated to\n\"device\" functions. These functions are *not* callable from the host via the\nCUDA API so a crate with only device functions is not too useful!\n\nOTOH, \"global\" functions *can* be called by the host; you can think of them\nas the real public API of your crate. To produce a global function use the\n`\"ptx-kernel\"` ABI.\n\n<!-- NOTE(ignore) this example is specific to the nvptx targets -->\n\n``` rust,ignore\n#![feature(abi_ptx)]\n#![no_std]\n\npub unsafe extern \"ptx-kernel\" fn global_function() {\n    device_function();\n}\n\npub fn device_function() {\n    // ..\n}\n```\n\n``` text\n$ xargo rustc --target nvptx64-nvidia-cuda --release -- --emit=asm\n\n$ cat $(find -name '*.s')\n//\n// Generated by LLVM NVPTX Back-End\n//\n\n.version 3.2\n.target sm_20\n.address_size 64\n\n        // .globl       _ZN6kernel15global_function17h46111ebe6516b382E\n\n.visible .entry _ZN6kernel15global_function17h46111ebe6516b382E()\n{\n\n\n        ret;\n}\n\n        // .globl       _ZN6kernel15device_function17hd6a0e4993bbf3f78E\n.visible .func _ZN6kernel15device_function17hd6a0e4993bbf3f78E()\n{\n\n\n        ret;\n}\n```\n" } , LintCompletion { label : "unsized_tuple_coercion" , description : "# `unsized_tuple_coercion`\n\nThe tracking issue for this feature is: [#42877]\n\n[#42877]: https://github.com/rust-lang/rust/issues/42877\n\n------------------------\n\nThis is a part of [RFC0401]. According to the RFC, there should be an implementation like this:\n\n```rust,ignore\nimpl<..., T, U: ?Sized> Unsized<(..., U)> for (..., T) where T: Unsized<U> {}\n```\n\nThis implementation is currently gated behind `#[feature(unsized_tuple_coercion)]` to avoid insta-stability. Therefore you can use it like this:\n\n```rust\n#![feature(unsized_tuple_coercion)]\n\nfn main() {\n    let x : ([i32; 3], [i32; 3]) = ([1, 2, 3], [4, 5, 6]);\n    let y : &([i32; 3], [i32]) = &x;\n    assert_eq!(y.1[0], 4);\n}\n```\n\n[RFC0401]: https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md\n" } , LintCompletion { label : "const_in_array_repeat_expressions" , description : "# `const_in_array_repeat_expressions`\n\nThe tracking issue for this feature is: [#49147]\n\n[#49147]: https://github.com/rust-lang/rust/issues/49147\n\n------------------------\n\nRelaxes the rules for repeat expressions, `[x; N]` such that `x` may also be `const` (strictly\nspeaking rvalue promotable), in addition to `typeof(x): Copy`. The result of `[x; N]` where `x` is\n`const` is itself also `const`.\n" } , LintCompletion { label : "impl_trait_in_bindings" , description : "# `impl_trait_in_bindings`\n\nThe tracking issue for this feature is: [#63065]\n\n[#63065]: https://github.com/rust-lang/rust/issues/63065\n\n------------------------\n\nThe `impl_trait_in_bindings` feature gate lets you use `impl Trait` syntax in\n`let`, `static`, and `const` bindings.\n\nA simple example is:\n\n```rust\n#![feature(impl_trait_in_bindings)]\n\nuse std::fmt::Debug;\n\nfn main() {\n    let a: impl Debug + Clone = 42;\n    let b = a.clone();\n    println!(\"{:?}\", b); // prints `42`\n}\n```\n\nNote however that because the types of `a` and `b` are opaque in the above\nexample, calling inherent methods or methods outside of the specified traits\n(e.g., `a.abs()` or `b.abs()`) is not allowed, and yields an error.\n" } , LintCompletion { label : "trait_alias" , description : "# `trait_alias`\n\nThe tracking issue for this feature is: [#41517]\n\n[#41517]: https://github.com/rust-lang/rust/issues/41517\n\n------------------------\n\nThe `trait_alias` feature adds support for trait aliases. These allow aliases\nto be created for one or more traits (currently just a single regular trait plus\nany number of auto-traits), and used wherever traits would normally be used as\neither bounds or trait objects.\n\n```rust\n#![feature(trait_alias)]\n\ntrait Foo = std::fmt::Debug + Send;\ntrait Bar = Foo + Sync;\n\n// Use trait alias as bound on type parameter.\nfn foo<T: Foo>(v: &T) {\n    println!(\"{:?}\", v);\n}\n\npub fn main() {\n    foo(&1);\n\n    // Use trait alias for trait objects.\n    let a: &Bar = &123;\n    println!(\"{:?}\", a);\n    let b = Box::new(456) as Box<dyn Foo>;\n    println!(\"{:?}\", b);\n}\n```\n" } , LintCompletion { label : "doc_cfg" , description : "# `doc_cfg`\n\nThe tracking issue for this feature is: [#43781]\n\n------\n\nThe `doc_cfg` feature allows an API be documented as only available in some specific platforms.\nThis attribute has two effects:\n\n1. In the annotated item's documentation, there will be a message saying \"This is supported on\n    (platform) only\".\n\n2. The item's doc-tests will only run on the specific platform.\n\nIn addition to allowing the use of the `#[doc(cfg)]` attribute, this feature enables the use of a\nspecial conditional compilation flag, `#[cfg(doc)]`, set whenever building documentation on your\ncrate.\n\nThis feature was introduced as part of PR [#43348] to allow the platform-specific parts of the\nstandard library be documented.\n\n```rust\n#![feature(doc_cfg)]\n\n#[cfg(any(windows, doc))]\n#[doc(cfg(windows))]\n/// The application's icon in the notification area (a.k.a. system tray).\n///\n/// # Examples\n///\n/// ```no_run\n/// extern crate my_awesome_ui_library;\n/// use my_awesome_ui_library::current_app;\n/// use my_awesome_ui_library::windows::notification;\n///\n/// let icon = current_app().get::<notification::Icon>();\n/// icon.show();\n/// icon.show_message(\"Hello\");\n/// ```\npub struct Icon {\n    // ...\n}\n```\n\n[#43781]: https://github.com/rust-lang/rust/issues/43781\n[#43348]: https://github.com/rust-lang/rust/issues/43348\n" } , LintCompletion { label : "lang_items" , description : "# `lang_items`\n\nThe tracking issue for this feature is: None.\n\n------------------------\n\nThe `rustc` compiler has certain pluggable operations, that is,\nfunctionality that isn't hard-coded into the language, but is\nimplemented in libraries, with a special marker to tell the compiler\nit exists. The marker is the attribute `#[lang = \"...\"]` and there are\nvarious different values of `...`, i.e. various different 'lang\nitems'.\n\nFor example, `Box` pointers require two lang items, one for allocation\nand one for deallocation. A freestanding program that uses the `Box`\nsugar for dynamic allocations via `malloc` and `free`:\n\n```rust,ignore\n#![feature(lang_items, box_syntax, start, libc, core_intrinsics)]\n#![no_std]\nuse core::intrinsics;\nuse core::panic::PanicInfo;\n\nextern crate libc;\n\n#[lang = \"owned_box\"]\npub struct Box<T>(*mut T);\n\n#[lang = \"exchange_malloc\"]\nunsafe fn allocate(size: usize, _align: usize) -> *mut u8 {\n    let p = libc::malloc(size as libc::size_t) as *mut u8;\n\n    // Check if `malloc` failed:\n    if p as usize == 0 {\n        intrinsics::abort();\n    }\n\n    p\n}\n\n#[lang = \"box_free\"]\nunsafe fn box_free<T: ?Sized>(ptr: *mut T) {\n    libc::free(ptr as *mut libc::c_void)\n}\n\n#[start]\nfn main(_argc: isize, _argv: *const *const u8) -> isize {\n    let _x = box 1;\n\n    0\n}\n\n#[lang = \"eh_personality\"] extern fn rust_eh_personality() {}\n#[lang = \"panic_impl\"] extern fn rust_begin_panic(info: &PanicInfo) -> ! { unsafe { intrinsics::abort() } }\n#[no_mangle] pub extern fn rust_eh_register_frames () {}\n#[no_mangle] pub extern fn rust_eh_unregister_frames () {}\n```\n\nNote the use of `abort`: the `exchange_malloc` lang item is assumed to\nreturn a valid pointer, and so needs to do the check internally.\n\nOther features provided by lang items include:\n\n- overloadable operators via traits: the traits corresponding to the\n  `==`, `<`, dereferencing (`*`) and `+` (etc.) operators are all\n  marked with lang items; those specific four are `eq`, `ord`,\n  `deref`, and `add` respectively.\n- stack unwinding and general failure; the `eh_personality`,\n  `panic` and `panic_bounds_checks` lang items.\n- the traits in `std::marker` used to indicate types of\n  various kinds; lang items `send`, `sync` and `copy`.\n- the marker types and variance indicators found in\n  `std::marker`; lang items `covariant_type`,\n  `contravariant_lifetime`, etc.\n\nLang items are loaded lazily by the compiler; e.g. if one never uses\n`Box` then there is no need to define functions for `exchange_malloc`\nand `box_free`. `rustc` will emit an error when an item is needed\nbut not found in the current crate or any that it depends on.\n\nMost lang items are defined by `libcore`, but if you're trying to build\nan executable without the standard library, you'll run into the need\nfor lang items. The rest of this page focuses on this use-case, even though\nlang items are a bit broader than that.\n\n### Using libc\n\nIn order to build a `#[no_std]` executable we will need libc as a dependency.\nWe can specify this using our `Cargo.toml` file:\n\n```toml\n[dependencies]\nlibc = { version = \"0.2.14\", default-features = false }\n```\n\nNote that the default features have been disabled. This is a critical step -\n**the default features of libc include the standard library and so must be\ndisabled.**\n\n### Writing an executable without stdlib\n\nControlling the entry point is possible in two ways: the `#[start]` attribute,\nor overriding the default shim for the C `main` function with your own.\n\nThe function marked `#[start]` is passed the command line parameters\nin the same format as C:\n\n```rust,ignore\n#![feature(lang_items, core_intrinsics)]\n#![feature(start)]\n#![no_std]\nuse core::intrinsics;\nuse core::panic::PanicInfo;\n\n// Pull in the system libc library for what crt0.o likely requires.\nextern crate libc;\n\n// Entry point for this program.\n#[start]\nfn start(_argc: isize, _argv: *const *const u8) -> isize {\n    0\n}\n\n// These functions are used by the compiler, but not\n// for a bare-bones hello world. These are normally\n// provided by libstd.\n#[lang = \"eh_personality\"]\n#[no_mangle]\npub extern fn rust_eh_personality() {\n}\n\n#[lang = \"panic_impl\"]\n#[no_mangle]\npub extern fn rust_begin_panic(info: &PanicInfo) -> ! {\n    unsafe { intrinsics::abort() }\n}\n```\n\nTo override the compiler-inserted `main` shim, one has to disable it\nwith `#![no_main]` and then create the appropriate symbol with the\ncorrect ABI and the correct name, which requires overriding the\ncompiler's name mangling too:\n\n```rust,ignore\n#![feature(lang_items, core_intrinsics)]\n#![feature(start)]\n#![no_std]\n#![no_main]\nuse core::intrinsics;\nuse core::panic::PanicInfo;\n\n// Pull in the system libc library for what crt0.o likely requires.\nextern crate libc;\n\n// Entry point for this program.\n#[no_mangle] // ensure that this symbol is called `main` in the output\npub extern fn main(_argc: i32, _argv: *const *const u8) -> i32 {\n    0\n}\n\n// These functions are used by the compiler, but not\n// for a bare-bones hello world. These are normally\n// provided by libstd.\n#[lang = \"eh_personality\"]\n#[no_mangle]\npub extern fn rust_eh_personality() {\n}\n\n#[lang = \"panic_impl\"]\n#[no_mangle]\npub extern fn rust_begin_panic(info: &PanicInfo) -> ! {\n    unsafe { intrinsics::abort() }\n}\n```\n\nIn many cases, you may need to manually link to the `compiler_builtins` crate\nwhen building a `no_std` binary. You may observe this via linker error messages\nsuch as \"```undefined reference to `__rust_probestack'```\".\n\n## More about the language items\n\nThe compiler currently makes a few assumptions about symbols which are\navailable in the executable to call. Normally these functions are provided by\nthe standard library, but without it you must define your own. These symbols\nare called \"language items\", and they each have an internal name, and then a\nsignature that an implementation must conform to.\n\nThe first of these functions, `rust_eh_personality`, is used by the failure\nmechanisms of the compiler. This is often mapped to GCC's personality function\n(see the [libstd implementation][unwind] for more information), but crates\nwhich do not trigger a panic can be assured that this function is never\ncalled. The language item's name is `eh_personality`.\n\n[unwind]: https://github.com/rust-lang/rust/blob/master/src/libpanic_unwind/gcc.rs\n\nThe second function, `rust_begin_panic`, is also used by the failure mechanisms of the\ncompiler. When a panic happens, this controls the message that's displayed on\nthe screen. While the language item's name is `panic_impl`, the symbol name is\n`rust_begin_panic`.\n\nFinally, a `eh_catch_typeinfo` static is needed for certain targets which\nimplement Rust panics on top of C++ exceptions.\n\n## List of all language items\n\nThis is a list of all language items in Rust along with where they are located in\nthe source code.\n\n- Primitives\n  - `i8`: `libcore/num/mod.rs`\n  - `i16`: `libcore/num/mod.rs`\n  - `i32`: `libcore/num/mod.rs`\n  - `i64`: `libcore/num/mod.rs`\n  - `i128`: `libcore/num/mod.rs`\n  - `isize`: `libcore/num/mod.rs`\n  - `u8`: `libcore/num/mod.rs`\n  - `u16`: `libcore/num/mod.rs`\n  - `u32`: `libcore/num/mod.rs`\n  - `u64`: `libcore/num/mod.rs`\n  - `u128`: `libcore/num/mod.rs`\n  - `usize`: `libcore/num/mod.rs`\n  - `f32`: `libstd/f32.rs`\n  - `f64`: `libstd/f64.rs`\n  - `char`: `libcore/char.rs`\n  - `slice`: `liballoc/slice.rs`\n  - `str`: `liballoc/str.rs`\n  - `const_ptr`: `libcore/ptr.rs`\n  - `mut_ptr`: `libcore/ptr