26 files changed, 564 insertions, 123 deletions

diff --git a/crates/ra_assists/src/assist_ctx.rs b/crates/ra_assists/src/assist_ctx.rs
index 2fe7c3de3..da2880037 100644
--- a/crates/ra_assists/src/assist_ctx.rs
+++ b/crates/ra_assists/src/assist_ctx.rs
@@ -105,7 +105,7 @@ impl<'a> AssistCtx<'a> {
         let mut info = AssistInfo::new(label);
         if self.should_compute_edit {
             let action = {
-                let mut edit = ActionBuilder::default();
+                let mut edit = ActionBuilder::new(&self);
                 f(&mut edit);
                 edit.build()
             };
@@ -130,6 +130,12 @@ impl<'a> AssistCtx<'a> {
     pub(crate) fn find_node_at_offset<N: AstNode>(&self) -> Option<N> {
         find_node_at_offset(self.source_file.syntax(), self.frange.range.start())
     }
+
+    pub(crate) fn find_node_at_offset_with_descend<N: AstNode>(&self) -> Option<N> {
+        self.sema
+            .find_node_at_offset_with_descend(self.source_file.syntax(), self.frange.range.start())
+    }
+
     pub(crate) fn covering_element(&self) -> SyntaxElement {
         find_covering_element(self.source_file.syntax(), self.frange.range)
     }
@@ -156,7 +162,7 @@ impl<'a> AssistGroup<'a> {
         let mut info = AssistInfo::new(label).with_group(GroupLabel(self.group_name.clone()));
         if self.ctx.should_compute_edit {
             let action = {
-                let mut edit = ActionBuilder::default();
+                let mut edit = ActionBuilder::new(&self.ctx);
                 f(&mut edit);
                 edit.build()
             };
@@ -175,15 +181,29 @@ impl<'a> AssistGroup<'a> {
     }
 }
 
-#[derive(Default)]
-pub(crate) struct ActionBuilder {
+pub(crate) struct ActionBuilder<'a, 'b> {
     edit: TextEditBuilder,
     cursor_position: Option<TextSize>,
     target: Option<TextRange>,
     file: AssistFile,
+    ctx: &'a AssistCtx<'b>,
 }
 
-impl ActionBuilder {
+impl<'a, 'b> ActionBuilder<'a, 'b> {
+    fn new(ctx: &'a AssistCtx<'b>) -> Self {
+        Self {
+            edit: TextEditBuilder::default(),
+            cursor_position: None,
+            target: None,
+            file: AssistFile::default(),
+            ctx,
+        }
+    }
+
+    pub(crate) fn ctx(&self) -> &AssistCtx<'b> {
+        &self.ctx
+    }
+
     /// Replaces specified `range` of text with a given string.
     pub(crate) fn replace(&mut self, range: TextRange, replace_with: impl Into<String>) {
         self.edit.replace(range, replace_with.into())
diff --git a/crates/ra_assists/src/handlers/auto_import.rs b/crates/ra_assists/src/handlers/auto_import.rs
index 99682e023..db6c4d2fa 100644
--- a/crates/ra_assists/src/handlers/auto_import.rs
+++ b/crates/ra_assists/src/handlers/auto_import.rs
@@ -45,15 +45,12 @@ pub(crate) fn auto_import(ctx: AssistCtx) -> Option<Assist> {
         return None;
     }
 
+    let range = ctx.sema.original_range(&auto_import_assets.syntax_under_caret).range;
     let mut group = ctx.add_assist_group(auto_import_assets.get_import_group_message());
     for import in proposed_imports {
         group.add_assist(AssistId("auto_import"), format!("Import `{}`", &import), |edit| {
-            edit.target(auto_import_assets.syntax_under_caret.text_range());
-            insert_use_statement(
-                &auto_import_assets.syntax_under_caret,
-                &import,
-                edit.text_edit_builder(),
-            );
+            edit.target(range);
+            insert_use_statement(&auto_import_assets.syntax_under_caret, &import, edit);
         });
     }
     group.finish()
@@ -68,10 +65,10 @@ struct AutoImportAssets {
 
 impl AutoImportAssets {
     fn new(ctx: &AssistCtx) -> Option<Self> {
-        if let Some(path_under_caret) = ctx.find_node_at_offset::<ast::Path>() {
+        if let Some(path_under_caret) = ctx.find_node_at_offset_with_descend::<ast::Path>() {
             Self::for_regular_path(path_under_caret, &ctx)
         } else {
-            Self::for_method_call(ctx.find_node_at_offset()?, &ctx)
+            Self::for_method_call(ctx.find_node_at_offset_with_descend()?, &ctx)
         }
     }
 
@@ -306,6 +303,35 @@ mod tests {
     }
 
     #[test]
+    fn applicable_when_found_an_import_in_macros() {
+        check_assist(
+            auto_import,
+            r"
+            macro_rules! foo {
+                ($i:ident) => { fn foo(a: $i) {} }
+            }
+            foo!(Pub<|>Struct);
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+            r"
+            use PubMod::PubStruct;
+
+            macro_rules! foo {
+                ($i:ident) => { fn foo(a: $i) {} }
+            }
+            foo!(Pub<|>Struct);
+
+            pub mod PubMod {
+                pub struct PubStruct;
+            }
+            ",
+        );
+    }
+
+    #[test]
     fn auto_imports_are_merged() {
         check_assist(
             auto_import,
diff --git a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
index 918e8dd8d..ff2463c77 100644
--- a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
+++ b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
@@ -38,7 +38,7 @@ pub(crate) fn replace_qualified_name_with_use(ctx: AssistCtx) -> Option<Assist>
         "Replace qualified path with use",
         |edit| {
             let path_to_import = hir_path.mod_path().clone();
-            insert_use_statement(path.syntax(), &path_to_import, edit.text_edit_builder());
+            insert_use_statement(path.syntax(), &path_to_import, edit);
 
             if let Some(last) = path.segment() {
                 // Here we are assuming the assist will provide a correct use statement
diff --git a/crates/ra_assists/src/utils.rs b/crates/ra_assists/src/utils.rs
index efd988697..6be704ce3 100644
--- a/crates/ra_assists/src/utils.rs
+++ b/crates/ra_assists/src/utils.rs
@@ -11,7 +11,7 @@ use ra_syntax::{
 };
 use rustc_hash::FxHashSet;
 
-pub use insert_use::insert_use_statement;
+pub(crate) use insert_use::insert_use_statement;
 
 pub fn get_missing_impl_items(
     sema: &Semantics<RootDatabase>,
diff --git a/crates/ra_assists/src/utils/insert_use.rs b/crates/ra_assists/src/utils/insert_use.rs
index c507e71e0..c1f447efe 100644
--- a/crates/ra_assists/src/utils/insert_use.rs
+++ b/crates/ra_assists/src/utils/insert_use.rs
@@ -2,6 +2,7 @@
 // FIXME: rewrite according to the plan, outlined in
 // https://github.com/rust-analyzer/rust-analyzer/issues/3301#issuecomment-592931553
 
+use crate::assist_ctx::ActionBuilder;
 use hir::{self, ModPath};
 use ra_syntax::{
     ast::{self, NameOwner},
@@ -14,14 +15,14 @@ use ra_text_edit::TextEditBuilder;
 /// Creates and inserts a use statement for the given path to import.
 /// The use statement is inserted in the scope most appropriate to the
 /// the cursor position given, additionally merged with the existing use imports.
-pub fn insert_use_statement(
+pub(crate) fn insert_use_statement(
     // Ideally the position of the cursor, used to
     position: &SyntaxNode,
     path_to_import: &ModPath,
-    edit: &mut TextEditBuilder,
+    edit: &mut ActionBuilder,
 ) {
     let target = path_to_import.to_string().split("::").map(SmolStr::new).collect::<Vec<_>>();
-    let container = position.ancestors().find_map(|n| {
+    let container = edit.ctx().sema.ancestors_with_macros(position.clone()).find_map(|n| {
         if let Some(module) = ast::Module::cast(n.clone()) {
             return module.item_list().map(|it| it.syntax().clone());
         }
@@ -30,7 +31,7 @@ pub fn insert_use_statement(
 
     if let Some(container) = container {
         let action = best_action_for_target(container, position.clone(), &target);
-        make_assist(&action, &target, edit);
+        make_assist(&action, &target, edit.text_edit_builder());
     }
 }
 
diff --git a/crates/ra_flycheck/Cargo.toml b/crates/ra_flycheck/Cargo.toml
index 324c33d9d..3d5093264 100644
--- a/crates/ra_flycheck/Cargo.toml
+++ b/crates/ra_flycheck/Cargo.toml
@@ -4,6 +4,9 @@ name = "ra_flycheck"
 version = "0.1.0"
 authors = ["rust-analyzer developers"]
 
+[lib]
+doctest = false
+
 [dependencies]
 crossbeam-channel = "0.4.0"
 lsp-types = { version = "0.74.0", features = ["proposed"] }
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index af59aa1b6..a004363ee 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -19,7 +19,7 @@ use hir_def::{
 use hir_expand::{
     diagnostics::DiagnosticSink,
     name::{name, AsName},
-    MacroDefId,
+    MacroDefId, MacroDefKind,
 };
 use hir_ty::{
     autoderef, display::HirFormatter, expr::ExprValidator, method_resolution, ApplicationTy,
@@ -762,13 +762,12 @@ impl MacroDef {
 
     /// Indicate it is a proc-macro
     pub fn is_proc_macro(&self) -> bool {
-        match self.id.kind {
-            hir_expand::MacroDefKind::Declarative => false,
-            hir_expand::MacroDefKind::BuiltIn(_) => false,
-            hir_expand::MacroDefKind::BuiltInDerive(_) => false,
-            hir_expand::MacroDefKind::BuiltInEager(_) => false,
-            hir_expand::MacroDefKind::CustomDerive(_) => true,
-        }
+        matches!(self.id.kind, MacroDefKind::CustomDerive(_))
+    }
+
+    /// Indicate it is a derive macro
+    pub fn is_derive_macro(&self) -> bool {
+        matches!(self.id.kind, MacroDefKind::CustomDerive(_) | MacroDefKind::BuiltInDerive(_))
     }
 }
 
diff --git a/crates/ra_hir_def/src/adt.rs b/crates/ra_hir_def/src/adt.rs
index 8eef51828..d0912ddaa 100644
--- a/crates/ra_hir_def/src/adt.rs
+++ b/crates/ra_hir_def/src/adt.rs
@@ -117,7 +117,13 @@ fn lower_enum(
     ast: &InFile<ast::EnumDef>,
     module_id: ModuleId,
 ) {
-    for var in ast.value.variant_list().into_iter().flat_map(|it| it.variants()) {
+    let expander = CfgExpander::new(db, ast.file_id, module_id.krate);
+    let variants =
+        ast.value.variant_list().into_iter().flat_map(|it| it.variants()).filter(|var| {
+            let attrs = expander.parse_attrs(var);
+            expander.is_cfg_enabled(&attrs)
+        });
+    for var in variants {
         trace.alloc(
             || var.clone(),
             || EnumVariantData {
diff --git a/crates/ra_hir_ty/src/tests.rs b/crates/ra_hir_ty/src/tests.rs
index 588d81282..d60732e19 100644
--- a/crates/ra_hir_ty/src/tests.rs
+++ b/crates/ra_hir_ty/src/tests.rs
@@ -361,6 +361,33 @@ fn no_such_field_with_feature_flag_diagnostics() {
 }
 
 #[test]
+fn no_such_field_enum_with_feature_flag_diagnostics() {
+    let diagnostics = TestDB::with_files(
+        r#"
+        //- /lib.rs crate:foo cfg:feature=foo
+        enum Foo {
+            #[cfg(not(feature = "foo"))]
+            Buz,
+            #[cfg(feature = "foo")]
+            Bar,
+            Baz
+        }
+
+        fn test_fn(f: Foo) {
+            match f {
+                Foo::Bar => {},
+                Foo::Baz => {},
+            }
+        }
+        "#,
+    )
+    .diagnostics()
+    .0;
+
+    assert_snapshot!(diagnostics, @r###""###);
+}
+
+#[test]
 fn no_such_field_with_feature_flag_diagnostics_on_struct_lit() {
     let diagnostics = TestDB::with_files(
         r#"
diff --git a/crates/ra_ide/src/completion.rs b/crates/ra_ide/src/completion.rs
index 4ca0fdf4f..a0e06faa2 100644
--- a/crates/ra_ide/src/completion.rs
+++ b/crates/ra_ide/src/completion.rs
@@ -65,21 +65,23 @@ pub(crate) fn completions(
     let ctx = CompletionContext::new(db, position, config)?;
 
     let mut acc = Completions::default();
-
-    complete_fn_param::complete_fn_param(&mut acc, &ctx);
-    complete_keyword::complete_expr_keyword(&mut acc, &ctx);
-    complete_keyword::complete_use_tree_keyword(&mut acc, &ctx);
-    complete_snippet::complete_expr_snippet(&mut acc, &ctx);
-    complete_snippet::complete_item_snippet(&mut acc, &ctx);
-    complete_qualified_path::complete_qualified_path(&mut acc, &ctx);
-    complete_unqualified_path::complete_unqualified_path(&mut acc, &ctx);
-    complete_dot::complete_dot(&mut acc, &ctx);
-    complete_record::complete_record(&mut acc, &ctx);
-    complete_pattern::complete_pattern(&mut acc, &ctx);
-    complete_postfix::complete_postfix(&mut acc, &ctx);
-    complete_macro_in_item_position::complete_macro_in_item_position(&mut acc, &ctx);
-    complete_trait_impl::complete_trait_impl(&mut acc, &ctx);
-    complete_attribute::complete_attribute(&mut acc, &ctx);
+    if ctx.attribute_under_caret.is_some() {
+        complete_attribute::complete_attribute(&mut acc, &ctx);
+    } else {
+        complete_fn_param::complete_fn_param(&mut acc, &ctx);
+        complete_keyword::complete_expr_keyword(&mut acc, &ctx);
+        complete_keyword::complete_use_tree_keyword(&mut acc, &ctx);
+        complete_snippet::complete_expr_snippet(&mut acc, &ctx);
+        complete_snippet::complete_item_snippet(&mut acc, &ctx);
+        complete_qualified_path::complete_qualified_path(&mut acc, &ctx);
+        complete_unqualified_path::complete_unqualified_path(&mut acc, &ctx);
+        complete_dot::complete_dot(&mut acc, &ctx);
+        complete_record::complete_record(&mut acc, &ctx);
+        complete_pattern::complete_pattern(&mut acc, &ctx);
+        complete_postfix::complete_postfix(&mut acc, &ctx);
+        complete_macro_in_item_position::complete_macro_in_item_position(&mut acc, &ctx);
+        complete_trait_impl::complete_trait_impl(&mut acc, &ctx);
+    }
 
     Some(acc)
 }
diff --git a/crates/ra_ide/src/completion/complete_attribute.rs b/crates/ra_ide/src/completion/complete_attribute.rs
index 8bf952798..20e6edc17 100644
--- a/crates/ra_ide/src/completion/complete_attribute.rs
+++ b/crates/ra_ide/src/completion/complete_attribute.rs
@@ -5,23 +5,26 @@
 
 use super::completion_context::CompletionContext;
 use super::completion_item::{CompletionItem, CompletionItemKind, CompletionKind, Completions};
+use ast::AttrInput;
 use ra_syntax::{
-    ast::{Attr, AttrKind},
-    AstNode,
+    ast::{self, AttrKind},
+    AstNode, SyntaxKind,
 };
+use rustc_hash::FxHashSet;
 
-pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext) {
-    if !ctx.is_attribute {
-        return;
-    }
+pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
+    let attribute = ctx.attribute_under_caret.as_ref()?;
 
-    let is_inner = ctx
-        .original_token
-        .ancestors()
-        .find_map(Attr::cast)
-        .map(|attr| attr.kind() == AttrKind::Inner)
-        .unwrap_or(false);
+    match (attribute.path(), attribute.input()) {
+        (Some(path), Some(AttrInput::TokenTree(token_tree))) if path.to_string() == "derive" => {
+            complete_derive(acc, ctx, token_tree)
+        }
+        _ => complete_attribute_start(acc, ctx, attribute),
+    }
+    Some(())
+}
 
+fn complete_attribute_start(acc: &mut Completions, ctx: &CompletionContext, attribute: &ast::Attr) {
     for attr_completion in ATTRIBUTES {
         let mut item = CompletionItem::new(
             CompletionKind::Attribute,
@@ -37,7 +40,7 @@ pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext)
             _ => {}
         }
 
-        if is_inner || !attr_completion.should_be_inner {
+        if attribute.kind() == AttrKind::Inner || !attr_completion.should_be_inner {
             acc.add(item);
         }
     }
@@ -126,6 +129,106 @@ const ATTRIBUTES: &[AttrCompletion] = &[
     },
 ];
 
+fn complete_derive(acc: &mut Completions, ctx: &CompletionContext, derive_input: ast::TokenTree) {
+    if let Ok(existing_derives) = parse_derive_input(derive_input) {
+        for derive_completion in DEFAULT_DERIVE_COMPLETIONS
+            .into_iter()
+            .filter(|completion| !existing_derives.contains(completion.label))
+        {
+            let mut label = derive_completion.label.to_owned();
+            for dependency in derive_completion
+                .dependencies
+                .into_iter()
+                .filter(|&&dependency| !existing_derives.contains(dependency))
+            {
+                label.push_str(", ");
+                label.push_str(dependency);
+            }
+            acc.add(
+                CompletionItem::new(CompletionKind::Attribute, ctx.source_range(), label)
+                    .kind(CompletionItemKind::Attribute),
+            );
+        }
+
+        for custom_derive_name in get_derive_names_in_scope(ctx).difference(&existing_derives) {
+            acc.add(
+                CompletionItem::new(
+                    CompletionKind::Attribute,
+                    ctx.source_range(),
+                    custom_derive_name,
+                )
+                .kind(CompletionItemKind::Attribute),
+            );
+        }
+    }
+}
+
+fn parse_derive_input(derive_input: ast::TokenTree) -> Result<FxHashSet<String>, ()> {
+    match (derive_input.left_delimiter_token(), derive_input.right_delimiter_token()) {
+        (Some(left_paren), Some(right_paren))
+            if left_paren.kind() == SyntaxKind::L_PAREN
+                && right_paren.kind() == SyntaxKind::R_PAREN =>
+        {
+            let mut input_derives = FxHashSet::default();
+            let mut current_derive = String::new();
+            for token in derive_input
+                .syntax()
+                .children_with_tokens()
+                .filter_map(|token| token.into_token())
+                .skip_while(|token| token != &left_paren)
+                .skip(1)
+                .take_while(|token| token != &right_paren)
+            {
+                if SyntaxKind::COMMA == token.kind() {
+                    if !current_derive.is_empty() {
+                        input_derives.insert(current_derive);
+                        current_derive = String::new();
+                    }
+                } else {
+                    current_derive.push_str(token.to_string().trim());
+                }
+            }
+
+            if !current_derive.is_empty() {
+                input_derives.insert(current_derive);
+            }
+            Ok(input_derives)
+        }
+        _ => Err(()),
+    }
+}
+
+fn get_derive_names_in_scope(ctx: &CompletionContext) -> FxHashSet<String> {
+    let mut result = FxHashSet::default();
+    ctx.scope().process_all_names(&mut |name, scope_def| {
+        if let hir::ScopeDef::MacroDef(mac) = scope_def {
+            if mac.is_derive_macro() {
+                result.insert(name.to_string());
+            }
+        }
+    });
+    result
+}
+
+struct DeriveCompletion {
+    label: &'static str,
+    dependencies: &'static [&'static str],
+}
+
+/// Standard Rust derives and the information about their dependencies
+/// (the dependencies are needed so that the main derive don't break the compilation when added)
+const DEFAULT_DERIVE_COMPLETIONS: &[DeriveCompletion] = &[
+    DeriveCompletion { label: "Clone", dependencies: &[] },
+    DeriveCompletion { label: "Copy", dependencies: &["Clone"] },
+    DeriveCompletion { label: "Debug", dependencies: &[] },
+    DeriveCompletion { label: "Default", dependencies: &[] },
+    DeriveCompletion { label: "Hash", dependencies: &[] },
+    DeriveCompletion { label: "PartialEq", dependencies: &[] },
+    DeriveCompletion { label: "Eq", dependencies: &["PartialEq"] },
+    DeriveCompletion { label: "PartialOrd", dependencies: &["PartialEq"] },
+    DeriveCompletion { label: "Ord", dependencies: &["PartialOrd", "Eq", "PartialEq"] },
+];
+
 #[cfg(test)]
 mod tests {
     use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
@@ -136,6 +239,170 @@ mod tests {
     }
 
     #[test]
+    fn empty_derive_completion() {
+        assert_debug_snapshot!(
+            do_attr_completion(
+                    r"
+                    #[derive(<|>)]
+                    struct Test {}
+                    ",
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "Clone",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Clone",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Copy, Clone",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Copy, Clone",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Debug",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Debug",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Default",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Default",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Eq, PartialEq",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Eq, PartialEq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Hash",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Hash",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Ord, PartialOrd, Eq, PartialEq",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Ord, PartialOrd, Eq, PartialEq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "PartialEq",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "PartialEq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "PartialOrd, PartialEq",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "PartialOrd, PartialEq",
+                kind: Attribute,
+            },
+        ]
+            "###
+        );
+    }
+
+    #[test]
+    fn no_completion_for_incorrect_derive() {
+        assert_debug_snapshot!(
+            do_attr_completion(
+                r"
+                    #[derive{<|>)]
+                    struct Test {}
+                    ",
+            ),
+            @"[]"
+        );
+    }
+
+    #[test]
+    fn derive_with_input_completion() {
+        assert_debug_snapshot!(
+            do_attr_completion(
+                    r"
+                    #[derive(serde::Serialize, PartialEq, <|>)]
+                    struct Test {}
+                    ",
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "Clone",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Clone",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Copy, Clone",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Copy, Clone",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Debug",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Debug",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Default",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Default",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Eq",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Eq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Hash",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Hash",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Ord, PartialOrd, Eq",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Ord, PartialOrd, Eq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "PartialOrd",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "PartialOrd",
+                kind: Attribute,
+            },
+        ]
+            "###
+        );
+    }
+
+    #[test]
     fn test_attribute_completion() {
         assert_debug_snapshot!(
         do_attr_completion(
diff --git a/crates/ra_ide/src/completion/completion_context.rs b/crates/ra_ide/src/completion/completion_context.rs
index c529752d4..dd87bd119 100644
--- a/crates/ra_ide/src/completion/completion_context.rs
+++ b/crates/ra_ide/src/completion/completion_context.rs
@@ -58,7 +58,7 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) is_macro_call: bool,
     pub(super) is_path_type: bool,
     pub(super) has_type_args: bool,
-    pub(super) is_attribute: bool,
+    pub(super) attribute_under_caret: Option<ast::Attr>,
 }
 
 impl<'a> CompletionContext<'a> {
@@ -116,7 +116,7 @@ impl<'a> CompletionContext<'a> {
             is_path_type: false,
             has_type_args: false,
             dot_receiver_is_ambiguous_float_literal: false,
-            is_attribute: false,
+            attribute_under_caret: None,
         };
 
         let mut original_file = original_file.syntax().clone();
@@ -200,6 +200,7 @@ impl<'a> CompletionContext<'a> {
                 Some(ty)
             })
             .flatten();
+        self.attribute_under_caret = find_node_at_offset(&file_with_fake_ident, offset);
 
         // First, let's try to complete a reference to some declaration.
         if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(&file_with_fake_ident, offset) {
@@ -318,7 +319,6 @@ impl<'a> CompletionContext<'a> {
                 .and_then(|it| it.syntax().parent().and_then(ast::CallExpr::cast))
                 .is_some();
             self.is_macro_call = path.syntax().parent().and_then(ast::MacroCall::cast).is_some();
-            self.is_attribute = path.syntax().parent().and_then(ast::Attr::cast).is_some();
 
             self.is_path_type = path.syntax().parent().and_then(ast::PathType::cast).is_some();
             self.has_type_args = segment.type_arg_list().is_some();
diff --git a/crates/ra_ide/src/display/navigation_target.rs b/crates/ra_ide/src/display/navigation_target.rs
index 914a8b471..de35c6711 100644
--- a/crates/ra_ide/src/display/navigation_target.rs
+++ b/crates/ra_ide/src/display/navigation_target.rs
@@ -376,16 +376,20 @@ impl ToNav for hir::Local {
 impl ToNav for hir::TypeParam {
     fn to_nav(&self, db: &RootDatabase) -> NavigationTarget {
         let src = self.source(db);
-        let range = match src.value {
+        let full_range = match &src.value {
             Either::Left(it) => it.syntax().text_range(),
             Either::Right(it) => it.syntax().text_range(),
         };
+        let focus_range = match &src.value {
+            Either::Left(_) => None,
+            Either::Right(it) => it.name().map(|it| it.syntax().text_range()),
+        };
         NavigationTarget {
             file_id: src.file_id.original_file(db),
             name: self.name(db).to_string().into(),
             kind: TYPE_PARAM,
-            full_range: range,
-            focus_range: None,
+            full_range,
+            focus_range,
             container_name: None,
             description: None,
             docs: None,
diff --git a/crates/ra_ide/src/goto_definition.rs b/crates/ra_ide/src/goto_definition.rs
index 5b9b3eef8..150895abb 100644
--- a/crates/ra_ide/src/goto_definition.rs
+++ b/crates/ra_ide/src/goto_definition.rs
@@ -787,14 +787,14 @@ mod tests {
     #[test]
     fn goto_for_type_param() {
         check_goto(
-            "
+            r#"
             //- /lib.rs
-            struct Foo<T> {
+            struct Foo<T: Clone> {
                 t: <|>T,
             }
-            ",
-            "T TYPE_PARAM FileId(1) 11..12",
-            "T",
+            "#,
+            "T TYPE_PARAM FileId(1) 11..19 11..12",
+            "T: Clone|T",
         );
     }
 
diff --git a/crates/ra_ide/src/inlay_hints.rs b/crates/ra_ide/src/inlay_hints.rs
index 98483df32..b391f903a 100644
--- a/crates/ra_ide/src/inlay_hints.rs
+++ b/crates/ra_ide/src/inlay_hints.rs
@@ -9,6 +9,7 @@ use ra_syntax::{
 };
 
 use crate::{FileId, FunctionSignature};
+use stdx::to_lower_snake_case;
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct InlayHintsConfig {
@@ -144,7 +145,7 @@ fn get_param_name_hints(
         .iter()
         .skip(n_params_to_skip)
         .zip(args)
-        .filter(|(param, arg)| should_show_param_hint(&fn_signature, param, &arg))
+        .filter(|(param, arg)| should_show_param_name_hint(sema, &fn_signature, param, &arg))
         .map(|(param_name, arg)| InlayHint {
             range: arg.syntax().text_range(),
             kind: InlayKind::ParameterHint,
@@ -181,7 +182,7 @@ fn get_bind_pat_hints(
 
 fn pat_is_enum_variant(db: &RootDatabase, bind_pat: &ast::BindPat, pat_ty: &Type) -> bool {
     if let Some(Adt::Enum(enum_data)) = pat_ty.as_adt() {
-        let pat_text = bind_pat.syntax().to_string();
+        let pat_text = bind_pat.to_string();
         enum_data
             .variants(db)
             .into_iter()
@@ -198,7 +199,7 @@ fn should_not_display_type_hint(db: &RootDatabase, bind_pat: &ast::BindPat, pat_
     }
 
     if let Some(Adt::Struct(s)) = pat_ty.as_adt() {
-        if s.fields(db).is_empty() && s.name(db).to_string() == bind_pat.syntax().to_string() {
+        if s.fields(db).is_empty() && s.name(db).to_string() == bind_pat.to_string() {
             return true;
         }
     }
@@ -230,15 +231,16 @@ fn should_not_display_type_hint(db: &RootDatabase, bind_pat: &ast::BindPat, pat_
     false
 }
 
-fn should_show_param_hint(
+fn should_show_param_name_hint(
+    sema: &Semantics<RootDatabase>,
     fn_signature: &FunctionSignature,
     param_name: &str,
     argument: &ast::Expr,
 ) -> bool {
+    let param_name = param_name.trim_start_matches('_');
     if param_name.is_empty()
-        || is_argument_similar_to_param(argument, param_name)
-        || Some(param_name.trim_start_matches('_'))
-            == fn_signature.name.as_ref().map(|s| s.trim_start_matches('_'))
+        || Some(param_name) == fn_signature.name.as_ref().map(|s| s.trim_start_matches('_'))
+        || is_argument_similar_to_param_name(sema, argument, param_name)
     {
         return false;
     }
@@ -254,20 +256,42 @@ fn should_show_param_hint(
     parameters_len != 1 || !is_obvious_param(param_name)
 }
 
-fn is_argument_similar_to_param(argument: &ast::Expr, param_name: &str) -> bool {
-    let argument_string = remove_ref(argument.clone()).syntax().to_string();
-    let param_name = param_name.trim_start_matches('_');
-    let argument_string = argument_string.trim_start_matches('_');
-    argument_string.starts_with(&param_name) || argument_string.ends_with(&param_name)
+fn is_argument_similar_to_param_name(
+    sema: &Semantics<RootDatabase>,
+    argument: &ast::Expr,
+    param_name: &str,
+) -> bool {
+    if is_enum_name_similar_to_param_name(sema, argument, param_name) {
+        return true;
+    }
+    match get_string_representation(argument) {
+        None => false,
+        Some(repr) => {
+            let argument_string = repr.trim_start_matches('_');
+            argument_string.starts_with(param_name) || argument_string.ends_with(param_name)
+        }
+    }
+}
+
+fn is_enum_name_similar_to_param_name(
+    sema: &Semantics<RootDatabase>,
+    argument: &ast::Expr,
+    param_name: &str,
+) -> bool {
+    match sema.type_of_expr(argument).and_then(|t| t.as_adt()) {
+        Some(Adt::Enum(e)) => to_lower_snake_case(&e.name(sema.db).to_string()) == param_name,
+        _ => false,
+    }
 }
 
-fn remove_ref(expr: ast::Expr) -> ast::Expr {
-    if let ast::Expr::RefExpr(ref_expr) = &expr {
-        if let Some(inner) = ref_expr.expr() {
-            return inner;
+fn get_string_representation(expr: &ast::Expr) -> Option<String> {
+    match expr {
+        ast::Expr::MethodCallExpr(method_call_expr) => {
+            Some(method_call_expr.name_ref()?.to_string())
         }
+        ast::Expr::RefExpr(ref_expr) => get_string_representation(&ref_expr.expr()?),
+        _ => Some(expr.to_string()),
     }
-    expr
 }
 
 fn is_obvious_param(param_name: &str) -> bool {
@@ -1073,6 +1097,12 @@ struct TestVarContainer {
     test_var: i32,
 }
 
+impl TestVarContainer {
+    fn test_var(&self) -> i32 {
+        self.test_var
+    }
+}
+
 struct Test {}
 
 impl Test {
@@ -1098,10 +1128,15 @@ struct Param {}
 fn different_order(param: &Param) {}
 fn different_order_mut(param: &mut Param) {}
 fn has_underscore(_param: bool) {}
+fn enum_matches_param_name(completion_kind: CompletionKind) {}
 
 fn twiddle(twiddle: bool) {}
 fn doo(_doo: bool) {}
 
+enum CompletionKind {
+    Keyword,
+}
+
 fn main() {
     let container: TestVarContainer = TestVarContainer { test_var: 42 };
     let test: Test = Test {};
@@ -1114,18 +1149,21 @@ fn main() {
     let test_var: i32 = 55;
     test_processed.no_hints_expected(22, test_var);
     test_processed.no_hints_expected(33, container.test_var);
+    test_processed.no_hints_expected(44, container.test_var());
     test_processed.frob(false);
 
     twiddle(true);
     doo(true);
 
-    let param_begin: Param = Param {};
+    let mut param_begin: Param = Param {};
     different_order(&param_begin);
     different_order(&mut param_begin);
 
     let param: bool = true;
     has_underscore(param);
 
+    enum_matches_param_name(CompletionKind::Keyword);
+
     let a: f64 = 7.0;
     let b: f64 = 4.0;
     let _: f64 = a.div_euclid(b);
diff --git a/crates/ra_ide/src/marks.rs b/crates/ra_ide/src/marks.rs
index bea30fe2a..51ca4dde3 100644
--- a/crates/ra_ide/src/marks.rs
+++ b/crates/ra_ide/src/marks.rs
@@ -11,4 +11,6 @@ test_utils::marks!(
     self_fulfilling_completion
     test_struct_field_completion_in_func_call
     test_struct_field_completion_in_record_lit
+    test_rename_struct_field_for_shorthand
+    test_rename_local_for_field_shorthand
 );
diff --git a/crates/ra_ide/src/references/rename.rs b/crates/ra_ide/src/references/rename.rs
index fd17bc9f2..916edaef2 100644
--- a/crates/ra_ide/src/references/rename.rs
+++ b/crates/ra_ide/src/references/rename.rs
@@ -7,14 +7,13 @@ use ra_syntax::{
     algo::find_node_at_offset, ast, lex_single_valid_syntax_kind, AstNode, SyntaxKind, SyntaxNode,
 };
 use ra_text_edit::TextEdit;
+use test_utils::tested_by;
 
 use crate::{
-    FilePosition, FileSystemEdit, RangeInfo, Reference, ReferenceKind, SourceChange,
-    SourceFileEdit, TextRange,
+    references::find_all_refs, FilePosition, FileSystemEdit, RangeInfo, Reference, ReferenceKind,
+    SourceChange, SourceFileEdit, TextRange,
 };
 
-use super::find_all_refs;
-
 pub(crate) fn rename(
     db: &RootDatabase,
     position: FilePosition,
@@ -52,11 +51,13 @@ fn source_edit_from_reference(reference: Reference, new_name: &str) -> SourceFil
     let file_id = reference.file_range.file_id;
     let range = match reference.kind {
         ReferenceKind::FieldShorthandForField => {
+            tested_by!(test_rename_struct_field_for_shorthand);
             replacement_text.push_str(new_name);
             replacement_text.push_str(": ");
             TextRange::new(reference.file_range.range.start(), reference.file_range.range.start())
         }
         ReferenceKind::FieldShorthandForLocal => {
+            tested_by!(test_rename_local_for_field_shorthand);
             replacement_text.push_str(": ");
             replacement_text.push_str(new_name);
             TextRange::new(reference.file_range.range.end(), reference.file_range.range.end())
@@ -147,7 +148,7 @@ fn rename_reference(
 mod tests {
     use insta::assert_debug_snapshot;
     use ra_text_edit::TextEditBuilder;
-    use test_utils::assert_eq_text;
+    use test_utils::{assert_eq_text, covers};
 
     use crate::{
         mock_analysis::analysis_and_position, mock_analysis::single_file_with_position, FileId,
@@ -379,6 +380,7 @@ mod tests {
 
     #[test]
     fn test_rename_struct_field_for_shorthand() {
+        covers!(test_rename_struct_field_for_shorthand);
         test_rename(
             r#"
     struct Foo {
@@ -408,6 +410,7 @@ mod tests {
 
     #[test]
     fn test_rename_local_for_field_shorthand() {
+        covers!(test_rename_local_for_field_shorthand);
         test_rename(
             r#"
     struct Foo {
diff --git a/crates/ra_ide_db/src/line_index.rs b/crates/ra_ide_db/src/line_index.rs
index 00ba95913..212cb7b5b 100644
--- a/crates/ra_ide_db/src/line_index.rs
+++ b/crates/ra_ide_db/src/line_index.rs
@@ -8,7 +8,9 @@ use superslice::Ext;
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct LineIndex {
+    /// Offset the the beginning of each line, zero-based
     pub(crate) newlines: Vec<TextSize>,
+    /// List of non-ASCII characters on each line
     pub(crate) utf16_lines: FxHashMap<u32, Vec<Utf16Char>>,
 }
 
@@ -22,7 +24,9 @@ pub struct LineCol {
 
 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
 pub(crate) struct Utf16Char {
+    /// Start offset of a character inside a line, zero-based
     pub(crate) start: TextSize,
+    /// End offset of a character inside a line, zero-based
     pub(crate) end: TextSize,
 }
 
@@ -120,7 +124,7 @@ impl LineIndex {
     fn utf16_to_utf8_col(&self, line: u32, mut col: u32) -> TextSize {
         if let Some(utf16_chars) = self.utf16_lines.get(&line) {
             for c in utf16_chars {
-                if col >= u32::from(c.start) {
+                if col > u32::from(c.start) {
                     col += u32::from(c.len()) - 1;
                 } else {
                     // From here on, all utf16 characters come *after* the character we are mapping,
@@ -226,8 +230,10 @@ const C: char = \"メ メ\";
         // UTF-16 to UTF-8
         assert_eq!(col_index.utf16_to_utf8_col(1, 15), TextSize::from(15));
 
-        assert_eq!(col_index.utf16_to_utf8_col(1, 18), TextSize::from(20));
-        assert_eq!(col_index.utf16_to_utf8_col(1, 19), TextSize::from(23));
+        // メ UTF-8: 0xE3 0x83 0xA1, UTF-16: 0x30E1
+        assert_eq!(col_index.utf16_to_utf8_col(1, 17), TextSize::from(17)); // first メ at 17..20
+        assert_eq!(col_index.utf16_to_utf8_col(1, 18), TextSize::from(20)); // space
+        assert_eq!(col_index.utf16_to_utf8_col(1, 19), TextSize::from(21)); // second メ at 21..24
 
         assert_eq!(col_index.utf16_to_utf8_col(2, 15), TextSize::from(15));
     }
diff --git a/crates/ra_syntax/src/ast/extensions.rs b/crates/ra_syntax/src/ast/extensions.rs
index 528c873e0..98c38d009 100644
--- a/crates/ra_syntax/src/ast/extensions.rs
+++ b/crates/ra_syntax/src/ast/extensions.rs
@@ -467,7 +467,7 @@ impl ast::TokenTree {
 
     pub fn right_delimiter_token(&self) -> Option<SyntaxToken> {
         self.syntax().last_child_or_token()?.into_token().filter(|it| match it.kind() {
-            T!['{'] | T!['('] | T!['['] => true,
+            T!['}'] | T![')'] | T![']'] => true,
             _ => false,
         })
     }
diff --git a/crates/ra_syntax/src/ast/generated/nodes.rs b/crates/ra_syntax/src/ast/generated/nodes.rs
index 5e844d5ae..c2cc25958 100644
--- a/crates/ra_syntax/src/ast/generated/nodes.rs
+++ b/crates/ra_syntax/src/ast/generated/nodes.rs
@@ -12,6 +12,7 @@ pub struct SourceFile {
 }
 impl ast::ModuleItemOwner for SourceFile {}
 impl ast::AttrsOwner for SourceFile {}
+impl ast::DocCommentsOwner for SourceFile {}
 impl SourceFile {
     pub fn modules(&self) -> AstChildren<Module> { support::children(&self.syntax) }
 }
@@ -259,6 +260,7 @@ pub struct ImplDef {
 }
 impl ast::TypeParamsOwner for ImplDef {}
 impl ast::AttrsOwner for ImplDef {}
+impl ast::DocCommentsOwner for ImplDef {}
 impl ImplDef {
     pub fn default_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![default]) }
     pub fn const_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![const]) }
diff --git a/crates/rust-analyzer/src/caps.rs b/crates/rust-analyzer/src/caps.rs
index 44222d8bd..680415cac 100644
--- a/crates/rust-analyzer/src/caps.rs
+++ b/crates/rust-analyzer/src/caps.rs
@@ -1,4 +1,5 @@
 //! Advertizes the capabilities of the LSP Server.
+use std::env;
 
 use crate::semantic_tokens;
 
@@ -16,7 +17,11 @@ pub fn server_capabilities() -> ServerCapabilities {
     ServerCapabilities {
         text_document_sync: Some(TextDocumentSyncCapability::Options(TextDocumentSyncOptions {
             open_close: Some(true),
-            change: Some(TextDocumentSyncKind::Incremental),
+            change: Some(if env::var("RA_PROFILE").is_ok() {
+                TextDocumentSyncKind::Incremental
+            } else {
+                TextDocumentSyncKind::Full
+            }),
             will_save: None,
             will_save_wait_until: None,
             save: Some(SaveOptions::default()),
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 3bc2e0a46..401fae755 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -666,6 +666,10 @@ fn apply_document_changes(
     mut line_index: Cow<'_, LineIndex>,
     content_changes: Vec<TextDocumentContentChangeEvent>,
 ) {
+    // Remove when https://github.com/rust-analyzer/rust-analyzer/issues/4263 is fixed.
+    let backup_text = old_text.clone();
+    let backup_changes = content_changes.clone();
+
     // The changes we got must be applied sequentially, but can cross lines so we
     // have to keep our line index updated.
     // Some clients (e.g. Code) sort the ranges in reverse. As an optimization, we
@@ -693,7 +697,19 @@ fn apply_document_changes(
                 }
                 index_valid = IndexValid::UpToLine(range.start.line);
                 let range = range.conv_with(&line_index);
-                old_text.replace_range(Range::<usize>::from(range), &change.text);
+                let mut text = old_text.to_owned();
+                match std::panic::catch_unwind(move || {
+                    text.replace_range(Range::<usize>::from(range), &change.text);
+                    text
+                }) {
+                    Ok(t) => *old_text = t,
+                    Err(e) => {
+                        eprintln!("Bug in incremental text synchronization. Please report the following output on https://github.com/rust-analyzer/rust-analyzer/issues/4263");
+                        dbg!(&backup_text);
+                        dbg!(&backup_changes);
+                        std::panic::resume_unwind(e);
+                    }
+                }
             }
             None => {
                 *old_text = change.text;
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index 01cdf452c..0f34ce70e 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -102,3 +102,17 @@ pub fn timeit(label: &'static str) -> impl Drop {
 
     Guard { label, start: Instant::now() }
 }
+
+pub fn to_lower_snake_case(s: &str) -> String {
+    let mut buf = String::with_capacity(s.len());
+    let mut prev = false;
+    for c in s.chars() {
+        if c.is_ascii_uppercase() && prev {
+            buf.push('_')
+        }
+        prev = true;
+
+        buf.push(c.to_ascii_lowercase());
+    }
+    buf
+}
diff --git a/docs/dev/debugging.md b/docs/dev/debugging.md
index bece6a572..1aa392935 100644
--- a/docs/dev/debugging.md
+++ b/docs/dev/debugging.md
@@ -26,7 +26,7 @@ where **only** the `rust-analyzer` extension being debugged is enabled.
 - `Run Extension (Dev Server)` - runs extension with the locally built LSP server (`target/debug/rust-analyzer`).
 
 TypeScript debugging is configured to watch your source edits and recompile.
-To apply changes to an already running debug process press <kbd>Ctrl+Shift+P</kbd> and run the following command in your `[Extension Development Host]`
+To apply changes to an already running debug process, press <kbd>Ctrl+Shift+P</kbd> and run the following command in your `[Extension Development Host]`
 
 ```
 > Developer: Reload Window
@@ -76,11 +76,11 @@ Make sure you open a rust file in the `[Extension Development Host]` and try aga
 
 Make sure you have run `echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope`.
 
-By default this should reset back to 1 everytime you log in.
+By default this should reset back to 1 every time you log in.
 
 ### Breakpoints are never being hit
 
-Check your version of `lldb` if it's version 6 and lower use the `classic` adapter type.
+Check your version of `lldb`. If it's version 6 and lower, use the `classic` adapter type.
 It's `lldb.adapterType` in settings file.
 
-If you're running `lldb` version 7 change the lldb adapter type to `bundled` or `native`.
+If you're running `lldb` version 7, change the lldb adapter type to `bundled` or `native`.
diff --git a/docs/dev/syntax.md b/docs/dev/syntax.md
index 33973ffec..c2864bbbc 100644
--- a/docs/dev/syntax.md
+++ b/docs/dev/syntax.md
@@ -64,7 +64,7 @@ struct Token {
 }
 ```
 
-All the difference bettwen the above sketch and the real implementation are strictly due to optimizations.
+All the difference between the above sketch and the real implementation are strictly due to optimizations.
 
 Points of note:
 * The tree is untyped. Each node has a "type tag", `SyntaxKind`.
@@ -72,7 +72,7 @@ Points of note:
 * Trivia and non-trivia tokens are not distinguished on the type level.
 * Each token carries its full text.
 * The original text can be recovered by concatenating the texts of all tokens in order.
-* Accessing a child of particular type (for example, parameter list of a function) generarly involves linerary traversing the children, looking for a specific `kind`.
+* Accessing a child of particular type (for example, parameter list of a function) generally involves linerary traversing the children, looking for a specific `kind`.
 * Modifying the tree is roughly `O(depth)`.
   We don't make special efforts to guarantree that the depth is not liner, but, in practice, syntax trees are branchy and shallow.
 * If mandatory (grammar wise) node is missing from the input, it's just missing from the tree.
@@ -123,7 +123,7 @@ To more compactly store the children, we box *both* interior nodes and tokens, a
 `Either<Arc<Node>, Arc<Token>>` as a single pointer with a tag in the last bit.
 
 To avoid allocating EVERY SINGLE TOKEN on the heap, syntax trees use interning.
-Because the tree is fully imutable, it's valid to structuraly share subtrees.
+Because the tree is fully immutable, it's valid to structurally share subtrees.
 For example, in `1 + 1`, there will be a *single* token for `1` with ref count 2; the same goes for the ` ` whitespace token.
 Interior nodes are shared as well (for example in `(1 + 1) * (1 + 1)`).
 
@@ -134,8 +134,8 @@ Currently, the interner is created per-file, but it will be easy to use a per-th
 
 We use a `TextSize`, a newtyped `u32`, to store the length of the text.
 
-We currently use `SmolStr`, an small object optimized string to store text.
-This was mostly relevant *before* we implmented tree interning, to avoid allocating common keywords and identifiers. We should switch to storing text data alongside the interned tokens.
+We currently use `SmolStr`, a small object optimized string to store text.
+This was mostly relevant *before* we implemented tree interning, to avoid allocating common keywords and identifiers. We should switch to storing text data alongside the interned tokens.
 
 #### Alternative designs
 
@@ -162,12 +162,12 @@ Explicit trivia nodes, like in `rowan`, are used by IntelliJ.
 
 ##### Accessing Children
 
-As noted before, accesing a specific child in the node requires a linear traversal of the children (though we can skip tokens, beacuse the tag is encoded in the pointer itself).
+As noted before, accessing a specific child in the node requires a linear traversal of the children (though we can skip tokens, because the tag is encoded in the pointer itself).
 It is possible to recover O(1) access with another representation.
 We explicitly store optional and missing (required by the grammar, but not present) nodes.
 That is, we use `Option<Node>` for children.
 We also remove trivia tokens from the tree.
-This way, each child kind genrerally occupies a fixed position in a parent, and we can use index access to fetch it.
+This way, each child kind generally occupies a fixed position in a parent, and we can use index access to fetch it.
 The cost is that we now need to allocate space for all not-present optional nodes.
 So, `fn foo() {}` will have slots for visibility, unsafeness, attributes, abi and return type.
 
@@ -193,7 +193,7 @@ Modeling this with immutable trees is possible, but annoying.
 ### Syntax Nodes
 
 A function green tree is not super-convenient to use.
-The biggest problem is acessing parents (there are no parent pointers!).
+The biggest problem is accessing parents (there are no parent pointers!).
 But there are also "identify" issues.
 Let's say you want to write a code which builds a list of expressions in a file: `fn collect_exrepssions(file: GreenNode) -> HashSet<GreenNode>`.
 For the input like
@@ -207,7 +207,7 @@ fn main() {
 }
 ```
 
-both copies of the `x + 2` expression are representing by equal (and, with interning in mind, actualy the same) green nodes.
+both copies of the `x + 2` expression are representing by equal (and, with interning in mind, actually the same) green nodes.
 Green trees just can't differentiate between the two.
 
 `SyntaxNode` adds parent pointers and identify semantics to green nodes.
@@ -285,9 +285,9 @@ They also point to the parent (and, consequently, to the root) with an owning `R
 In other words, one needs *one* arc bump when initiating a traversal.
 
 To get rid of allocations, `rowan` takes advantage of `SyntaxNode: !Sync` and uses a thread-local free list of `SyntaxNode`s.
-In a typical traversal, you only directly hold a few `SyntaxNode`s at a time (and their ancesstors indirectly), so a free list proportional to the depth of the tree removes all allocations in a typical case.
+In a typical traversal, you only directly hold a few `SyntaxNode`s at a time (and their ancestors indirectly), so a free list proportional to the depth of the tree removes all allocations in a typical case.
 
-So, while traversal is not exactly incrementing a pointer, it's still prety cheep: tls + rc bump!
+So, while traversal is not exactly incrementing a pointer, it's still pretty cheap: TLS + rc bump!
 
 Traversal also yields (cheap) owned nodes, which improves ergonomics quite a bit.
 
@@ -308,15 +308,15 @@ struct SyntaxData {
 }
 ```
 
-This allows using true pointer equality for comparision of identities of `SyntaxNodes`.
-rust-analyzer used to have this design as well, but since we've switch to cursors.
-The main problem with memoizing the red nodes is that it more than doubles the memory requirenments for fully realized syntax trees.
+This allows using true pointer equality for comparison of identities of `SyntaxNodes`.
+rust-analyzer used to have this design as well, but we've since switched to cursors.
+The main problem with memoizing the red nodes is that it more than doubles the memory requirements for fully realized syntax trees.
 In contrast, cursors generally retain only a path to the root.
 C# combats increased memory usage by using weak references.
 
 ### AST
 
-`GreenTree`s are untyped and homogeneous, because it makes accomodating error nodes, arbitrary whitespace and comments natural, and because it makes possible to write generic tree traversals.
+`GreenTree`s are untyped and homogeneous, because it makes accommodating error nodes, arbitrary whitespace and comments natural, and because it makes possible to write generic tree traversals.
 However, when working with a specific node, like a function definition, one would want a strongly typed API.
 
 This is what is provided by the AST layer. AST nodes are transparent wrappers over untyped syntax nodes:
@@ -397,7 +397,7 @@ impl HasVisbility for FnDef {
 Points of note:
 
 * Like `SyntaxNode`s, AST nodes are cheap to clone pointer-sized owned values.
-* All "fields" are optional, to accomodate incomplete and/or erroneous source code.
+* All "fields" are optional, to accommodate incomplete and/or erroneous source code.
 * It's always possible to go from an ast node to an untyped `SyntaxNode`.
 * It's possible to go in the opposite direction with a checked cast.
 * `enum`s allow modeling of arbitrary intersecting subsets of AST types.
@@ -437,13 +437,13 @@ impl GreenNodeBuilder {
 }
 ```
 
-The parser, ultimatelly, needs to invoke the `GreenNodeBuilder`.
+The parser, ultimately, needs to invoke the `GreenNodeBuilder`.
 There are two principal sources of inputs for the parser:
   * source text, which contains trivia tokens (whitespace and comments)
   * token trees from macros, which lack trivia
 
-Additionaly, input tokens do not correspond 1-to-1 with output tokens.
-For example, two consequtive `>` tokens might be glued, by the parser, into a single `>>`.
+Additionally, input tokens do not correspond 1-to-1 with output tokens.
+For example, two consecutive `>` tokens might be glued, by the parser, into a single `>>`.
 
 For these reasons, the parser crate defines a callback interfaces for both input tokens and output trees.
 The explicit glue layer then bridges various gaps.
@@ -491,7 +491,7 @@ Syntax errors are not stored directly in the tree.
 The primary motivation for this is that syntax tree is not necessary produced by the parser, it may also be assembled manually from pieces (which happens all the time in refactorings).
 Instead, parser reports errors to an error sink, which stores them in a `Vec`.
 If possible, errors are not reported during parsing and are postponed for a separate validation step.
-For example, parser accepts visibility modifiers on trait methods, but then a separate tree traversal flags all such visibilites as erroneous.
+For example, parser accepts visibility modifiers on trait methods, but then a separate tree traversal flags all such visibilities as erroneous.
 
 ### Macros
 
@@ -501,7 +501,7 @@ Specifically, `TreeSink` constructs the tree in lockstep with draining the origi
 In the process, it records which tokens of the tree correspond to which tokens of the input, by using text ranges to identify syntax tokens.
 The end result is that parsing an expanded code yields a syntax tree and a mapping of text-ranges of the tree to original tokens.
 
-To deal with precedence in cases like `$expr * 1`, we use special invisible parenthesis, which are explicitelly handled by the parser
+To deal with precedence in cases like `$expr * 1`, we use special invisible parenthesis, which are explicitly handled by the parser
 
 ### Whitespace & Comments
 
diff --git a/xtask/src/ast_src.rs b/xtask/src/ast_src.rs
index 028f7cbe1..2f8065b73 100644
--- a/xtask/src/ast_src.rs
+++ b/xtask/src/ast_src.rs
@@ -305,7 +305,7 @@ macro_rules! ast_enums {
 pub(crate) const AST_SRC: AstSrc = AstSrc {
     tokens: &["Whitespace", "Comment", "String", "RawString"],
     nodes: &ast_nodes! {
-        struct SourceFile: ModuleItemOwner, AttrsOwner {
+        struct SourceFile: ModuleItemOwner, AttrsOwner, DocCommentsOwner {
             modules: [Module],
         }
 
@@ -401,7 +401,7 @@ pub(crate) const AST_SRC: AstSrc = AstSrc {
             T![;]
         }
 
-        struct ImplDef: TypeParamsOwner, AttrsOwner {
+        struct ImplDef: TypeParamsOwner, AttrsOwner, DocCommentsOwner {
             T![default],
             T![const],
             T![unsafe],