Merge #6430

6430: Move completions rendering into a separate module r=popzxc a=popzxc

This PR extracts rendering-related things from `Completions` structure to the new `render` module.

`render` module declares a `Render` structure (which is a generic renderer interface), `RenderContext` (interface for data/methods not required for completions generating, but required for rendering), and a bunch of smaller `*Render` structures which encapsulate logic behind rendering a certain item.

This is just a step in full separation direction, since the following this are still to be done:

- Move some data from `CompletionContext` to the `RenderContext`;
- Forbid any kind of rendering outside of `render` module;
- Extract score computing into a separate module.

This PR is already pretty big, so not to make it even harder to review I decided to split this process into several subsequent PRs.


Co-authored-by: Igor Aleksanov <popzxc@yandex.ru>

crates/completion/src/context.rs

@@ -245,19 +245,6 @@ impl<'a> CompletionContext<'a> {
         }
     }
 
-    pub(crate) fn active_name_and_type(&self) -> Option<(String, Type)> {
-        if let Some(record_field) = &self.record_field_syntax {
-            mark::hit!(record_field_type_match);
-            let (struct_field, _local) = self.sema.resolve_record_field(record_field)?;
-            Some((struct_field.name(self.db).to_string(), struct_field.signature_ty(self.db)))
-        } else if let Some(active_parameter) = &self.active_parameter {
-            mark::hit!(active_param_type_match);
-            Some((active_parameter.name.clone(), active_parameter.ty.clone()))
-        } else {
-            None
-        }
-    }
-
     fn fill_keyword_patterns(&mut self, file_with_fake_ident: &SyntaxNode, offset: TextSize) {
         let fake_ident_token = file_with_fake_ident.token_at_offset(offset).right_biased().unwrap();
         let syntax_element = NodeOrToken::Token(fake_ident_token);

crates/completion/src/lib.rs

@@ -7,6 +7,7 @@ mod patterns;
 mod generated_lint_completions;
 #[cfg(test)]
 mod test_utils;
+mod render;
 
 mod completions;
 

crates/completion/src/render.rs

@@ -0,0 +1,848 @@
+//! `render` module provides utilities for rendering completion suggestions
+//! into code pieces that will be presented to user.
+
+pub(crate) mod macro_;
+pub(crate) mod function;
+pub(crate) mod enum_variant;
+pub(crate) mod const_;
+pub(crate) mod type_alias;
+
+mod builder_ext;
+
+use hir::{Documentation, HasAttrs, HirDisplay, Mutability, ScopeDef, Type};
+use ide_db::RootDatabase;
+use syntax::TextRange;
+use test_utils::mark;
+
+use crate::{
+    config::SnippetCap, CompletionContext, CompletionItem, CompletionItemKind, CompletionKind,
+    CompletionScore,
+};
+
+use crate::render::{enum_variant::render_enum_variant, function::render_fn, macro_::render_macro};
+
+pub(crate) fn render_field<'a>(
+    ctx: RenderContext<'a>,
+    field: hir::Field,
+    ty: &Type,
+) -> CompletionItem {
+    Render::new(ctx).add_field(field, ty)
+}
+
+pub(crate) fn render_tuple_field<'a>(
+    ctx: RenderContext<'a>,
+    field: usize,
+    ty: &Type,
+) -> CompletionItem {
+    Render::new(ctx).add_tuple_field(field, ty)
+}
+
+pub(crate) fn render_resolution<'a>(
+    ctx: RenderContext<'a>,
+    local_name: String,
+    resolution: &ScopeDef,
+) -> Option<CompletionItem> {
+    Render::new(ctx).render_resolution(local_name, resolution)
+}
+
+/// Interface for data and methods required for items rendering.
+#[derive(Debug)]
+pub(crate) struct RenderContext<'a> {
+    completion: &'a CompletionContext<'a>,
+}
+
+impl<'a> RenderContext<'a> {
+    pub(crate) fn new(completion: &'a CompletionContext<'a>) -> RenderContext<'a> {
+        RenderContext { completion }
+    }
+
+    fn snippet_cap(&self) -> Option<SnippetCap> {
+        self.completion.config.snippet_cap.clone()
+    }
+
+    fn db(&self) -> &'a RootDatabase {
+        &self.completion.db
+    }
+
+    fn source_range(&self) -> TextRange {
+        self.completion.source_range()
+    }
+
+    fn is_deprecated(&self, node: impl HasAttrs) -> bool {
+        node.attrs(self.db()).by_key("deprecated").exists()
+    }
+
+    fn docs(&self, node: impl HasAttrs) -> Option<Documentation> {
+        node.docs(self.db())
+    }
+
+    fn active_name_and_type(&self) -> Option<(String, Type)> {
+        if let Some(record_field) = &self.completion.record_field_syntax {
+            mark::hit!(record_field_type_match);
+            let (struct_field, _local) = self.completion.sema.resolve_record_field(record_field)?;
+            Some((struct_field.name(self.db()).to_string(), struct_field.signature_ty(self.db())))
+        } else if let Some(active_parameter) = &self.completion.active_parameter {
+            mark::hit!(active_param_type_match);
+            Some((active_parameter.name.clone(), active_parameter.ty.clone()))
+        } else {
+            None
+        }
+    }
+}
+
+/// Generic renderer for completion items.
+#[derive(Debug)]
+struct Render<'a> {
+    ctx: RenderContext<'a>,
+}
+
+impl<'a> Render<'a> {
+    fn new(ctx: RenderContext<'a>) -> Render<'a> {
+        Render { ctx }
+    }
+
+    fn add_field(&mut self, field: hir::Field, ty: &Type) -> CompletionItem {
+        let is_deprecated = self.ctx.is_deprecated(field);
+        let name = field.name(self.ctx.db());
+        let mut item = CompletionItem::new(
+            CompletionKind::Reference,
+            self.ctx.source_range(),
+            name.to_string(),
+        )
+        .kind(CompletionItemKind::Field)
+        .detail(ty.display(self.ctx.db()).to_string())
+        .set_documentation(field.docs(self.ctx.db()))
+        .set_deprecated(is_deprecated);
+
+        if let Some(score) = compute_score(&self.ctx, &ty, &name.to_string()) {
+            item = item.set_score(score);
+        }
+
+        item.build()
+    }
+
+    fn add_tuple_field(&mut self, field: usize, ty: &Type) -> CompletionItem {
+        CompletionItem::new(CompletionKind::Reference, self.ctx.source_range(), field.to_string())
+            .kind(CompletionItemKind::Field)
+            .detail(ty.display(self.ctx.db()).to_string())
+            .build()
+    }
+
+    fn render_resolution(
+        self,
+        local_name: String,
+        resolution: &ScopeDef,
+    ) -> Option<CompletionItem> {
+        use hir::ModuleDef::*;
+
+        let completion_kind = match resolution {
+            ScopeDef::ModuleDef(BuiltinType(..)) => CompletionKind::BuiltinType,
+            _ => CompletionKind::Reference,
+        };
+
+        let kind = match resolution {
+            ScopeDef::ModuleDef(Function(func)) => {
+                let item = render_fn(self.ctx, Some(local_name), *func);
+                return Some(item);
+            }
+            ScopeDef::ModuleDef(EnumVariant(var)) => {
+                let item = render_enum_variant(self.ctx, Some(local_name), *var, None);
+                return Some(item);
+            }
+            ScopeDef::MacroDef(mac) => {
+                let item = render_macro(self.ctx, local_name, *mac);
+                return item;
+            }
+
+            ScopeDef::ModuleDef(Module(..)) => CompletionItemKind::Module,
+            ScopeDef::ModuleDef(Adt(hir::Adt::Struct(_))) => CompletionItemKind::Struct,
+            // FIXME: add CompletionItemKind::Union
+            ScopeDef::ModuleDef(Adt(hir::Adt::Union(_))) => CompletionItemKind::Struct,
+            ScopeDef::ModuleDef(Adt(hir::Adt::Enum(_))) => CompletionItemKind::Enum,
+            ScopeDef::ModuleDef(Const(..)) => CompletionItemKind::Const,
+            ScopeDef::ModuleDef(Static(..)) => CompletionItemKind::Static,
+            ScopeDef::ModuleDef(Trait(..)) => CompletionItemKind::Trait,
+            ScopeDef::ModuleDef(TypeAlias(..)) => CompletionItemKind::TypeAlias,
+            ScopeDef::ModuleDef(BuiltinType(..)) => CompletionItemKind::BuiltinType,
+            ScopeDef::GenericParam(..) => CompletionItemKind::TypeParam,
+            ScopeDef::Local(..) => CompletionItemKind::Binding,
+            // (does this need its own kind?)
+            ScopeDef::AdtSelfType(..) | ScopeDef::ImplSelfType(..) => CompletionItemKind::TypeParam,
+            ScopeDef::Unknown => {
+                let item = CompletionItem::new(
+                    CompletionKind::Reference,
+                    self.ctx.source_range(),
+                    local_name,
+                )
+                .kind(CompletionItemKind::UnresolvedReference)
+                .build();
+                return Some(item);
+            }
+        };
+
+        let docs = self.docs(resolution);
+
+        let mut item =
+            CompletionItem::new(completion_kind, self.ctx.source_range(), local_name.clone());
+        if let ScopeDef::Local(local) = resolution {
+            let ty = local.ty(self.ctx.db());
+            if !ty.is_unknown() {
+                item = item.detail(ty.display(self.ctx.db()).to_string());
+            }
+        };
+
+        let mut ref_match = None;
+        if let ScopeDef::Local(local) = resolution {
+            if let Some((active_name, active_type)) = self.ctx.active_name_and_type() {
+                let ty = local.ty(self.ctx.db());
+                if let Some(score) =
+                    compute_score_from_active(&active_type, &active_name, &ty, &local_name)
+                {
+                    item = item.set_score(score);
+                }
+                ref_match = refed_type_matches(&active_type, &active_name, &ty, &local_name);
+            }
+        }
+
+        // Add `<>` for generic types
+        if self.ctx.completion.is_path_type
+            && !self.ctx.completion.has_type_args
+            && self.ctx.completion.config.add_call_parenthesis
+        {
+            if let Some(cap) = self.ctx.snippet_cap() {
+                let has_non_default_type_params = match resolution {
+                    ScopeDef::ModuleDef(Adt(it)) => it.has_non_default_type_params(self.ctx.db()),
+                    ScopeDef::ModuleDef(TypeAlias(it)) => {
+                        it.has_non_default_type_params(self.ctx.db())
+                    }
+                    _ => false,
+                };
+                if has_non_default_type_params {
+                    mark::hit!(inserts_angle_brackets_for_generics);
+                    item = item
+                        .lookup_by(local_name.clone())
+                        .label(format!("{}<…>", local_name))
+                        .insert_snippet(cap, format!("{}<$0>", local_name));
+                }
+            }
+        }
+
+        let item = item.kind(kind).set_documentation(docs).set_ref_match(ref_match).build();
+        Some(item)
+    }
+
+    fn docs(&self, resolution: &ScopeDef) -> Option<Documentation> {
+        use hir::ModuleDef::*;
+        match resolution {
+            ScopeDef::ModuleDef(Module(it)) => it.docs(self.ctx.db()),
+            ScopeDef::ModuleDef(Adt(it)) => it.docs(self.ctx.db()),
+            ScopeDef::ModuleDef(EnumVariant(it)) => it.docs(self.ctx.db()),
+            ScopeDef::ModuleDef(Const(it)) => it.docs(self.ctx.db()),
+            ScopeDef::ModuleDef(Static(it)) => it.docs(self.ctx.db()),
+            ScopeDef::ModuleDef(Trait(it)) => it.docs(self.ctx.db()),
+            ScopeDef::ModuleDef(TypeAlias(it)) => it.docs(self.ctx.db()),
+            _ => None,
+        }
+    }
+}
+
+fn compute_score_from_active(
+    active_type: &Type,
+    active_name: &str,
+    ty: &Type,
+    name: &str,
+) -> Option<CompletionScore> {
+    // Compute score
+    // For the same type
+    if active_type != ty {
+        return None;
+    }
+
+    let mut res = CompletionScore::TypeMatch;
+
+    // If same type + same name then go top position
+    if active_name == name {
+        res = CompletionScore::TypeAndNameMatch
+    }
+
+    Some(res)
+}
+fn refed_type_matches(
+    active_type: &Type,
+    active_name: &str,
+    ty: &Type,
+    name: &str,
+) -> Option<(Mutability, CompletionScore)> {
+    let derefed_active = active_type.remove_ref()?;
+    let score = compute_score_from_active(&derefed_active, &active_name, &ty, &name)?;
+    Some((
+        if active_type.is_mutable_reference() { Mutability::Mut } else { Mutability::Shared },
+        score,
+    ))
+}
+
+fn compute_score(ctx: &RenderContext, ty: &Type, name: &str) -> Option<CompletionScore> {
+    let (active_name, active_type) = ctx.active_name_and_type()?;
+    compute_score_from_active(&active_type, &active_name, ty, name)
+}
+
+#[cfg(test)]
+mod tests {
+    use std::cmp::Reverse;
+
+    use expect_test::{expect, Expect};
+    use test_utils::mark;
+
+    use crate::{
+        test_utils::{check_edit, do_completion, get_all_items},
+        CompletionConfig, CompletionKind, CompletionScore,
+    };
+
+    fn check(ra_fixture: &str, expect: Expect) {
+        let actual = do_completion(ra_fixture, CompletionKind::Reference);
+        expect.assert_debug_eq(&actual);
+    }
+
+    fn check_scores(ra_fixture: &str, expect: Expect) {
+        fn display_score(score: Option<CompletionScore>) -> &'static str {
+            match score {
+                Some(CompletionScore::TypeMatch) => "[type]",
+                Some(CompletionScore::TypeAndNameMatch) => "[type+name]",
+                None => "[]".into(),
+            }
+        }
+
+        let mut completions = get_all_items(CompletionConfig::default(), ra_fixture);
+        completions.sort_by_key(|it| (Reverse(it.score()), it.label().to_string()));
+        let actual = completions
+            .into_iter()
+            .filter(|it| it.completion_kind == CompletionKind::Reference)
+            .map(|it| {
+                let tag = it.kind().unwrap().tag();
+                let score = display_score(it.score());
+                format!("{} {} {}\n", tag, it.label(), score)
+            })
+            .collect::<String>();
+        expect.assert_eq(&actual);
+    }
+
+    #[test]
+    fn enum_detail_includes_record_fields() {
+        check(
+            r#"
+enum Foo { Foo { x: i32, y: i32 } }
+
+fn main() { Foo::Fo<|> }
+"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "Foo",
+                        source_range: 54..56,
+                        delete: 54..56,
+                        insert: "Foo",
+                        kind: EnumVariant,
+                        detail: "{ x: i32, y: i32 }",
+                    },
+                ]
+            "#]],
+        );
+    }
+
+    #[test]
+    fn enum_detail_doesnt_include_tuple_fields() {
+        check(
+            r#"
+enum Foo { Foo (i32, i32) }
+
+fn main() { Foo::Fo<|> }
+"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "Foo(…)",
+                        source_range: 46..48,
+                        delete: 46..48,
+                        insert: "Foo($0)",
+                        kind: EnumVariant,
+                        lookup: "Foo",
+                        detail: "(i32, i32)",
+                        trigger_call_info: true,
+                    },
+                ]
+            "#]],
+        );
+    }
+
+    #[test]
+    fn enum_detail_just_parentheses_for_unit() {
+        check(
+            r#"
+enum Foo { Foo }
+
+fn main() { Foo::Fo<|> }
+"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "Foo",
+                        source_range: 35..37,
+                        delete: 35..37,
+                        insert: "Foo",
+                        kind: EnumVariant,
+                        detail: "()",
+                    },
+                ]
+            "#]],
+        );
+    }
+
+    #[test]
+    fn lookup_enums_by_two_qualifiers() {
+        check(
+            r#"
+mod m {
+    pub enum Spam { Foo, Bar(i32) }
+}
+fn main() { let _: m::Spam = S<|> }
+"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "Spam::Bar(…)",
+                        source_range: 75..76,
+                        delete: 75..76,
+                        insert: "Spam::Bar($0)",
+                        kind: EnumVariant,
+                        lookup: "Spam::Bar",
+                        detail: "(i32)",
+                        trigger_call_info: true,
+                    },
+                    CompletionItem {
+                        label: "m",
+                        source_range: 75..76,
+                        delete: 75..76,
+                        insert: "m",
+                        kind: Module,
+                    },
+                    CompletionItem {
+                        label: "m::Spam::Foo",
+                        source_range: 75..76,
+                        delete: 75..76,
+                        insert: "m::Spam::Foo",
+                        kind: EnumVariant,
+                        lookup: "Spam::Foo",
+                        detail: "()",
+                    },
+                    CompletionItem {
+                        label: "main()",
+                        source_range: 75..76,
+                        delete: 75..76,
+                        insert: "main()$0",
+                        kind: Function,
+                        lookup: "main",
+                        detail: "fn main()",
+                    },
+                ]
+            "#]],
+        )
+    }
+
+    #[test]
+    fn sets_deprecated_flag_in_items() {
+        check(
+            r#"
+#[deprecated]
+fn something_deprecated() {}
+#[deprecated(since = "1.0.0")]
+fn something_else_deprecated() {}
+
+fn main() { som<|> }
+"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "main()",
+                        source_range: 121..124,
+                        delete: 121..124,
+                        insert: "main()$0",
+                        kind: Function,
+                        lookup: "main",
+                        detail: "fn main()",
+                    },
+                    CompletionItem {
+                        label: "something_deprecated()",
+                        source_range: 121..124,
+                        delete: 121..124,
+                        insert: "something_deprecated()$0",
+                        kind: Function,
+                        lookup: "something_deprecated",
+                        detail: "fn something_deprecated()",
+                        deprecated: true,
+                    },
+                    CompletionItem {
+                        label: "something_else_deprecated()",
+                        source_range: 121..124,
+                        delete: 121..124,
+                        insert: "something_else_deprecated()$0",
+                        kind: Function,
+                        lookup: "something_else_deprecated",
+                        detail: "fn something_else_deprecated()",
+                        deprecated: true,
+                    },
+                ]
+            "#]],
+        );
+
+        check(
+            r#"
+struct A { #[deprecated] the_field: u32 }
+fn foo() { A { the<|> } }
+"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "the_field",
+                        source_range: 57..60,
+                        delete: 57..60,
+                        insert: "the_field",
+                        kind: Field,
+                        detail: "u32",
+                        deprecated: true,
+                    },
+                ]
+            "#]],
+        );
+    }
+
+    #[test]
+    fn renders_docs() {
+        check(
+            r#"
+struct S {
+    /// Field docs
+    foo:
+}
+impl S {
+    /// Method docs
+    fn bar(self) { self.<|> }
+}"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "bar()",
+                        source_range: 94..94,
+                        delete: 94..94,
+                        insert: "bar()$0",
+                        kind: Method,
+                        lookup: "bar",
+                        detail: "fn bar(self)",
+                        documentation: Documentation(
+                            "Method docs",
+                        ),
+                    },
+                    CompletionItem {
+                        label: "foo",
+                        source_range: 94..94,
+                        delete: 94..94,
+                        insert: "foo",
+                        kind: Field,
+                        detail: "{unknown}",
+                        documentation: Documentation(
+                            "Field docs",
+                        ),
+                    },
+                ]
+            "#]],
+        );
+
+        check(
+            r#"
+use self::my<|>;
+
+/// mod docs
+mod my { }
+
+/// enum docs
+enum E {
+    /// variant docs
+    V
+}
+use self::E::*;
+"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "E",
+                        source_range: 10..12,
+                        delete: 10..12,
+                        insert: "E",
+                        kind: Enum,
+                        documentation: Documentation(
+                            "enum docs",
+                        ),
+                    },
+                    CompletionItem {
+                        label: "V",
+                        source_range: 10..12,
+                        delete: 10..12,
+                        insert: "V",
+                        kind: EnumVariant,
+                        detail: "()",
+                        documentation: Documentation(
+                            "variant docs",
+                        ),
+                    },
+                    CompletionItem {
+                        label: "my",
+                        source_range: 10..12,
+                        delete: 10..12,
+                        insert: "my",
+                        kind: Module,
+                        documentation: Documentation(
+                            "mod docs",
+                        ),
+                    },
+                ]
+            "#]],
+        )
+    }
+
+    #[test]
+    fn dont_render_attrs() {
+        check(
+            r#"
+struct S;
+impl S {
+    #[inline]
+    fn the_method(&self) { }
+}
+fn foo(s: S) { s.<|> }
+"#,
+            expect![[r#"
+                [
+                    CompletionItem {
+                        label: "the_method()",
+                        source_range: 81..81,
+                        delete: 81..81,
+                        insert: "the_method()$0",
+                        kind: Method,
+                        lookup: "the_method",
+                        detail: "fn the_method(&self)",
+                    },
+                ]
+            "#]],
+        )
+    }
+
+    #[test]
+    fn no_call_parens_if_fn_ptr_needed() {
+        mark::check!(no_call_parens_if_fn_ptr_needed);
+        check_edit(
+            "foo",
+            r#"
+fn foo(foo: u8, bar: u8) {}
+struct ManualVtable { f: fn(u8, u8) }
+
+fn main() -> ManualVtable {
+    ManualVtable { f: f<|> }
+}
+"#,
+            r#"
+fn foo(foo: u8, bar: u8) {}
+struct ManualVtable { f: fn(u8, u8) }
+
+fn main() -> ManualVtable {
+    ManualVtable { f: foo }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn no_parens_in_use_item() {
+        mark::check!(no_parens_in_use_item);
+        check_edit(
+            "foo",
+            r#"
+mod m { pub fn foo() {} }
+use crate::m::f<|>;
+"#,
+            r#"
+mod m { pub fn foo() {} }
+use crate::m::foo;
+"#,
+        );
+    }
+
+    #[test]
+    fn no_parens_in_call() {
+        check_edit(
+            "foo",
+            r#"
+fn foo(x: i32) {}
+fn main() { f<|>(); }
+"#,
+            r#"
+fn foo(x: i32) {}
+fn main() { foo(); }
+"#,
+        );
+        check_edit(
+            "foo",
+            r#"
+struct Foo;
+impl Foo { fn foo(&self){} }
+fn f(foo: &Foo) { foo.f<|>(); }
+"#,
+            r#"
+struct Foo;
+impl Foo { fn foo(&self){} }
+fn f(foo: &Foo) { foo.foo(); }
+"#,
+        );
+    }
+
+    #[test]
+    fn inserts_angle_brackets_for_generics() {
+        mark::check!(inserts_angle_brackets_for_generics);
+        check_edit(
+            "Vec",
+            r#"
+struct Vec<T> {}
+fn foo(xs: Ve<|>)
+"#,
+            r#"
+struct Vec<T> {}
+fn foo(xs: Vec<$0>)
+"#,
+        );
+        check_edit(
+            "Vec",
+            r#"
+type Vec<T> = (T,);
+fn foo(xs: Ve<|>)
+"#,
+            r#"
+type Vec<T> = (T,);
+fn foo(xs: Vec<$0>)
+"#,
+        );
+        check_edit(
+            "Vec",
+            r#"
+struct Vec<T = i128> {}
+fn foo(xs: Ve<|>)
+"#,
+            r#"
+struct Vec<T = i128> {}
+fn foo(xs: Vec)
+"#,
+        );
+        check_edit(
+            "Vec",
+            r#"
+struct Vec<T> {}
+fn foo(xs: Ve<|><i128>)
+"#,
+            r#"
+struct Vec<T> {}
+fn foo(xs: Vec<i128>)
+"#,
+        );
+    }
+
+    #[test]
+    fn active_param_score() {
+        mark::check!(active_param_type_match);
+        check_scores(
+            r#"
+struct S { foo: i64, bar: u32, baz: u32 }
+fn test(bar: u32) { }
+fn foo(s: S) { test(s.<|>) }
+"#,
+            expect![[r#"
+                fd bar [type+name]
+                fd baz [type]
+                fd foo []
+            "#]],
+        );
+    }
+
+    #[test]
+    fn record_field_scores() {
+        mark::check!(record_field_type_match);
+        check_scores(
+            r#"
+struct A { foo: i64, bar: u32, baz: u32 }
+struct B { x: (), y: f32, bar: u32 }
+fn foo(a: A) { B { bar: a.<|> }; }
+"#,
+            expect![[r#"
+                fd bar [type+name]
+                fd baz [type]
+                fd foo []
+            "#]],
+        )
+    }
+
+    #[test]
+    fn record_field_and_call_scores() {
+        check_scores(
+            r#"
+struct A { foo: i64, bar: u32, baz: u32 }
+struct B { x: (), y: f32, bar: u32 }
+fn f(foo: i64) {  }
+fn foo(a: A) { B { bar: f(a.<|>) }; }
+"#,
+            expect![[r#"
+                fd foo [type+name]
+                fd bar []
+                fd baz []
+            "#]],
+        );
+        check_scores(
+            r#"
+struct A { foo: i64, bar: u32, baz: u32 }
+struct B { x: (), y: f32, bar: u32 }
+fn f(foo: i64) {  }
+fn foo(a: A) { f(B { bar: a.<|> }); }
+"#,
+            expect![[r#"
+                fd bar [type+name]
+                fd baz [type]
+                fd foo []
+            "#]],
+        );
+    }
+
+    #[test]
+    fn prioritize_exact_ref_match() {
+        check_scores(
+            r#"
+struct WorldSnapshot { _f: () };
+fn go(world: &WorldSnapshot) { go(w<|>) }
+"#,
+            expect![[r#"
+                bn world [type+name]
+                st WorldSnapshot []
+                fn go(…) []
+            "#]],
+        );
+    }
+
+    #[test]
+    fn too_many_arguments() {
+        check_scores(
+            r#"
+struct Foo;
+fn f(foo: &Foo) { f(foo, w<|>) }
+"#,
+            expect![[r#"
+                st Foo []
+                fn f(…) []
+                bn foo []
+            "#]],
+        );
+    }
+}

crates/completion/src/render/builder_ext.rs

@@ -0,0 +1,94 @@
+//! Extensions for `Builder` structure required for item rendering.
+
+use itertools::Itertools;
+use test_utils::mark;
+
+use crate::{item::Builder, CompletionContext};
+
+pub(super) enum Params {
+    Named(Vec<String>),
+    Anonymous(usize),
+}
+
+impl Params {
+    pub(super) fn len(&self) -> usize {
+        match self {
+            Params::Named(xs) => xs.len(),
+            Params::Anonymous(len) => *len,
+        }
+    }
+
+    pub(super) fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+}
+
+impl Builder {
+    pub(super) fn should_add_parems(&self, ctx: &CompletionContext) -> bool {
+        if !ctx.config.add_call_parenthesis {
+            return false;
+        }
+        if ctx.use_item_syntax.is_some() {
+            mark::hit!(no_parens_in_use_item);
+            return false;
+        }
+        if ctx.is_pattern_call {
+            mark::hit!(dont_duplicate_pattern_parens);
+            return false;
+        }
+        if ctx.is_call {
+            return false;
+        }
+
+        // Don't add parentheses if the expected type is some function reference.
+        if let Some(ty) = &ctx.expected_type {
+            if ty.is_fn() {
+                mark::hit!(no_call_parens_if_fn_ptr_needed);
+                return false;
+            }
+        }
+
+        // Nothing prevents us from adding parentheses
+        true
+    }
+
+    pub(super) fn add_call_parens(
+        mut self,
+        ctx: &CompletionContext,
+        name: String,
+        params: Params,
+    ) -> Builder {
+        if !self.should_add_parems(ctx) {
+            return self;
+        }
+
+        let cap = match ctx.config.snippet_cap {
+            Some(it) => it,
+            None => return self,
+        };
+        // If not an import, add parenthesis automatically.
+        mark::hit!(inserts_parens_for_function_calls);
+
+        let (snippet, label) = if params.is_empty() {
+            (format!("{}()$0", name), format!("{}()", name))
+        } else {
+            self = self.trigger_call_info();
+            let snippet = match (ctx.config.add_call_argument_snippets, params) {
+                (true, Params::Named(params)) => {
+                    let function_params_snippet =
+                        params.iter().enumerate().format_with(", ", |(index, param_name), f| {
+                            f(&format_args!("${{{}:{}}}", index + 1, param_name))
+                        });
+                    format!("{}({})$0", name, function_params_snippet)
+                }
+                _ => {
+                    mark::hit!(suppress_arg_snippets);
+                    format!("{}($0)", name)
+                }
+            };
+
+            (snippet, format!("{}(…)", name))
+        };
+        self.lookup_by(name).label(label).insert_snippet(cap, snippet)
+    }
+}

crates/completion/src/render/const_.rs

@@ -0,0 +1,55 @@
+//! Renderer for `const` fields.
+
+use hir::HasSource;
+use syntax::{
+    ast::{Const, NameOwner},
+    display::const_label,
+};
+
+use crate::{
+    item::{CompletionItem, CompletionItemKind, CompletionKind},
+    render::RenderContext,
+};
+
+pub(crate) fn render_const<'a>(
+    ctx: RenderContext<'a>,
+    const_: hir::Const,
+) -> Option<CompletionItem> {
+    ConstRender::new(ctx, const_).render()
+}
+
+#[derive(Debug)]
+struct ConstRender<'a> {
+    ctx: RenderContext<'a>,
+    const_: hir::Const,
+    ast_node: Const,
+}
+
+impl<'a> ConstRender<'a> {
+    fn new(ctx: RenderContext<'a>, const_: hir::Const) -> ConstRender<'a> {
+        let ast_node = const_.source(ctx.db()).value;
+        ConstRender { ctx, const_, ast_node }
+    }
+
+    fn render(self) -> Option<CompletionItem> {
+        let name = self.name()?;
+        let detail = self.detail();
+
+        let item = CompletionItem::new(CompletionKind::Reference, self.ctx.source_range(), name)
+            .kind(CompletionItemKind::Const)
+            .set_documentation(self.ctx.docs(self.const_))
+            .set_deprecated(self.ctx.is_deprecated(self.const_))
+            .detail(detail)
+            .build();
+
+        Some(item)
+    }
+
+    fn name(&self) -> Option<String> {
+        self.ast_node.name().map(|name| name.text().to_string())
+    }
+
+    fn detail(&self) -> String {
+        const_label(&self.ast_node)
+    }
+}

crates/completion/src/render/enum_variant.rs

@@ -0,0 +1,180 @@
+//! Renderer for `enum` variants.
+
+use hir::{HasAttrs, HirDisplay, ModPath, StructKind};
+use itertools::Itertools;
+use test_utils::mark;
+
+use crate::{
+    item::{CompletionItem, CompletionItemKind, CompletionKind},
+    render::{builder_ext::Params, RenderContext},
+};
+
+pub(crate) fn render_enum_variant<'a>(
+    ctx: RenderContext<'a>,
+    local_name: Option<String>,
+    variant: hir::EnumVariant,
+    path: Option<ModPath>,
+) -> CompletionItem {
+    EnumVariantRender::new(ctx, local_name, variant, path).render()
+}
+
+#[derive(Debug)]
+struct EnumVariantRender<'a> {
+    ctx: RenderContext<'a>,
+    name: String,
+    variant: hir::EnumVariant,
+    path: Option<ModPath>,
+    qualified_name: String,
+    short_qualified_name: String,
+    variant_kind: StructKind,
+}
+
+impl<'a> EnumVariantRender<'a> {
+    fn new(
+        ctx: RenderContext<'a>,
+        local_name: Option<String>,
+        variant: hir::EnumVariant,
+        path: Option<ModPath>,
+    ) -> EnumVariantRender<'a> {
+        let name = local_name.unwrap_or_else(|| variant.name(ctx.db()).to_string());
+        let variant_kind = variant.kind(ctx.db());
+
+        let (qualified_name, short_qualified_name) = match &path {
+            Some(path) => {
+                let full = path.to_string();
+                let short =
+                    path.segments[path.segments.len().saturating_sub(2)..].iter().join("::");
+                (full, short)
+            }
+            None => (name.to_string(), name.to_string()),
+        };
+
+        EnumVariantRender {
+            ctx,
+            name,
+            variant,
+            path,
+            qualified_name,
+            short_qualified_name,
+            variant_kind,
+        }
+    }
+
+    fn render(self) -> CompletionItem {
+        let mut builder = CompletionItem::new(
+            CompletionKind::Reference,
+            self.ctx.source_range(),
+            self.qualified_name.clone(),
+        )
+        .kind(CompletionItemKind::EnumVariant)
+        .set_documentation(self.variant.docs(self.ctx.db()))
+        .set_deprecated(self.ctx.is_deprecated(self.variant))
+        .detail(self.detail());
+
+        if self.variant_kind == StructKind::Tuple {
+            mark::hit!(inserts_parens_for_tuple_enums);
+            let params = Params::Anonymous(self.variant.fields(self.ctx.db()).len());
+            builder =
+                builder.add_call_parens(self.ctx.completion, self.short_qualified_name, params);
+        } else if self.path.is_some() {
+            builder = builder.lookup_by(self.short_qualified_name);
+        }
+
+        builder.build()
+    }
+
+    fn detail(&self) -> String {
+        let detail_types = self
+            .variant
+            .fields(self.ctx.db())
+            .into_iter()
+            .map(|field| (field.name(self.ctx.db()), field.signature_ty(self.ctx.db())));
+
+        match self.variant_kind {
+            StructKind::Tuple | StructKind::Unit => format!(
+                "({})",
+                detail_types.map(|(_, t)| t.display(self.ctx.db()).to_string()).format(", ")
+            ),
+            StructKind::Record => format!(
+                "{{ {} }}",
+                detail_types
+                    .map(|(n, t)| format!("{}: {}", n, t.display(self.ctx.db()).to_string()))
+                    .format(", ")
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::mark;
+
+    use crate::test_utils::check_edit;
+
+    #[test]
+    fn inserts_parens_for_tuple_enums() {
+        mark::check!(inserts_parens_for_tuple_enums);
+        check_edit(
+            "Some",
+            r#"
+enum Option<T> { Some(T), None }
+use Option::*;
+fn main() -> Option<i32> {
+    Som<|>
+}
+"#,
+            r#"
+enum Option<T> { Some(T), None }
+use Option::*;
+fn main() -> Option<i32> {
+    Some($0)
+}
+"#,
+        );
+        check_edit(
+            "Some",
+            r#"
+enum Option<T> { Some(T), None }
+use Option::*;
+fn main(value: Option<i32>) {
+    match value {
+        Som<|>
+    }
+}
+"#,
+            r#"
+enum Option<T> { Some(T), None }
+use Option::*;
+fn main(value: Option<i32>) {
+    match value {
+        Some($0)
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn dont_duplicate_pattern_parens() {
+        mark::check!(dont_duplicate_pattern_parens);
+        check_edit(
+            "Var",
+            r#"
+enum E { Var(i32) }
+fn main() {
+    match E::Var(92) {
+        E::<|>(92) => (),
+    }
+}
+"#,
+            r#"
+enum E { Var(i32) }
+fn main() {
+    match E::Var(92) {
+        E::Var(92) => (),
+    }
+}
+"#,
+        );
+    }
+}

crates/completion/src/render/function.rs

@@ -0,0 +1,303 @@
+//! Renderer for function calls.
+
+use hir::{HasSource, Type};
+use syntax::{ast::Fn, display::function_declaration};
+
+use crate::{
+    item::{CompletionItem, CompletionItemKind, CompletionKind},
+    render::{builder_ext::Params, RenderContext},
+};
+
+pub(crate) fn render_fn<'a>(
+    ctx: RenderContext<'a>,
+    local_name: Option<String>,
+    fn_: hir::Function,
+) -> CompletionItem {
+    FunctionRender::new(ctx, local_name, fn_).render()
+}
+
+#[derive(Debug)]
+struct FunctionRender<'a> {
+    ctx: RenderContext<'a>,
+    name: String,
+    fn_: hir::Function,
+    ast_node: Fn,
+}
+
+impl<'a> FunctionRender<'a> {
+    fn new(
+        ctx: RenderContext<'a>,
+        local_name: Option<String>,
+        fn_: hir::Function,
+    ) -> FunctionRender<'a> {
+        let name = local_name.unwrap_or_else(|| fn_.name(ctx.db()).to_string());
+        let ast_node = fn_.source(ctx.db()).value;
+
+        FunctionRender { ctx, name, fn_, ast_node }
+    }
+
+    fn render(self) -> CompletionItem {
+        let params = self.params();
+        CompletionItem::new(CompletionKind::Reference, self.ctx.source_range(), self.name.clone())
+            .kind(self.kind())
+            .set_documentation(self.ctx.docs(self.fn_))
+            .set_deprecated(self.ctx.is_deprecated(self.fn_))
+            .detail(self.detail())
+            .add_call_parens(self.ctx.completion, self.name, params)
+            .build()
+    }
+
+    fn detail(&self) -> String {
+        function_declaration(&self.ast_node)
+    }
+
+    fn add_arg(&self, arg: &str, ty: &Type) -> String {
+        if let Some(derefed_ty) = ty.remove_ref() {
+            for (name, local) in self.ctx.completion.locals.iter() {
+                if name == arg && local.ty(self.ctx.db()) == derefed_ty {
+                    let mutability = if ty.is_mutable_reference() { "&mut " } else { "&" };
+                    return format!("{}{}", mutability, arg);
+                }
+            }
+        }
+        arg.to_string()
+    }
+
+    fn params(&self) -> Params {
+        let params_ty = self.fn_.params(self.ctx.db());
+        let params = self
+            .ast_node
+            .param_list()
+            .into_iter()
+            .flat_map(|it| it.params())
+            .zip(params_ty)
+            .flat_map(|(it, param_ty)| {
+                if let Some(pat) = it.pat() {
+                    let name = pat.to_string();
+                    let arg = name.trim_start_matches("mut ").trim_start_matches('_');
+                    return Some(self.add_arg(arg, param_ty.ty()));
+                }
+                None
+            })
+            .collect();
+        Params::Named(params)
+    }
+
+    fn kind(&self) -> CompletionItemKind {
+        if self.fn_.self_param(self.ctx.db()).is_some() {
+            CompletionItemKind::Method
+        } else {
+            CompletionItemKind::Function
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::mark;
+
+    use crate::{
+        test_utils::{check_edit, check_edit_with_config},
+        CompletionConfig,
+    };
+
+    #[test]
+    fn inserts_parens_for_function_calls() {
+        mark::check!(inserts_parens_for_function_calls);
+        check_edit(
+            "no_args",
+            r#"
+fn no_args() {}
+fn main() { no_<|> }
+"#,
+            r#"
+fn no_args() {}
+fn main() { no_args()$0 }
+"#,
+        );
+
+        check_edit(
+            "with_args",
+            r#"
+fn with_args(x: i32, y: String) {}
+fn main() { with_<|> }
+"#,
+            r#"
+fn with_args(x: i32, y: String) {}
+fn main() { with_args(${1:x}, ${2:y})$0 }
+"#,
+        );
+
+        check_edit(
+            "foo",
+            r#"
+struct S;
+impl S {
+    fn foo(&self) {}
+}
+fn bar(s: &S) { s.f<|> }
+"#,
+            r#"
+struct S;
+impl S {
+    fn foo(&self) {}
+}
+fn bar(s: &S) { s.foo()$0 }
+"#,
+        );
+
+        check_edit(
+            "foo",
+            r#"
+struct S {}
+impl S {
+    fn foo(&self, x: i32) {}
+}
+fn bar(s: &S) {
+    s.f<|>
+}
+"#,
+            r#"
+struct S {}
+impl S {
+    fn foo(&self, x: i32) {}
+}
+fn bar(s: &S) {
+    s.foo(${1:x})$0
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn suppress_arg_snippets() {
+        mark::check!(suppress_arg_snippets);
+        check_edit_with_config(
+            CompletionConfig { add_call_argument_snippets: false, ..CompletionConfig::default() },
+            "with_args",
+            r#"
+fn with_args(x: i32, y: String) {}
+fn main() { with_<|> }
+"#,
+            r#"
+fn with_args(x: i32, y: String) {}
+fn main() { with_args($0) }
+"#,
+        );
+    }
+
+    #[test]
+    fn strips_underscores_from_args() {
+        check_edit(
+            "foo",
+            r#"
+fn foo(_foo: i32, ___bar: bool, ho_ge_: String) {}
+fn main() { f<|> }
+"#,
+            r#"
+fn foo(_foo: i32, ___bar: bool, ho_ge_: String) {}
+fn main() { foo(${1:foo}, ${2:bar}, ${3:ho_ge_})$0 }
+"#,
+        );
+    }
+
+    #[test]
+    fn insert_ref_when_matching_local_in_scope() {
+        check_edit(
+            "ref_arg",
+            r#"
+struct Foo {}
+fn ref_arg(x: &Foo) {}
+fn main() {
+    let x = Foo {};
+    ref_ar<|>
+}
+"#,
+            r#"
+struct Foo {}
+fn ref_arg(x: &Foo) {}
+fn main() {
+    let x = Foo {};
+    ref_arg(${1:&x})$0
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn insert_mut_ref_when_matching_local_in_scope() {
+        check_edit(
+            "ref_arg",
+            r#"
+struct Foo {}
+fn ref_arg(x: &mut Foo) {}
+fn main() {
+    let x = Foo {};
+    ref_ar<|>
+}
+"#,
+            r#"
+struct Foo {}
+fn ref_arg(x: &mut Foo) {}
+fn main() {
+    let x = Foo {};
+    ref_arg(${1:&mut x})$0
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn insert_ref_when_matching_local_in_scope_for_method() {
+        check_edit(
+            "apply_foo",
+            r#"
+struct Foo {}
+struct Bar {}
+impl Bar {
+    fn apply_foo(&self, x: &Foo) {}
+}
+
+fn main() {
+    let x = Foo {};
+    let y = Bar {};
+    y.<|>
+}
+"#,
+            r#"
+struct Foo {}
+struct Bar {}
+impl Bar {
+    fn apply_foo(&self, x: &Foo) {}
+}
+
+fn main() {
+    let x = Foo {};
+    let y = Bar {};
+    y.apply_foo(${1:&x})$0
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn trim_mut_keyword_in_func_completion() {
+        check_edit(
+            "take_mutably",
+            r#"
+fn take_mutably(mut x: &i32) {}
+
+fn main() {
+    take_m<|>
+}
+"#,
+            r#"
+fn take_mutably(mut x: &i32) {}
+
+fn main() {
+    take_mutably(${1:x})$0
+}
+"#,
+        );
+    }
+}

crates/completion/src/render/macro_.rs

@@ -0,0 +1,216 @@
+//! Renderer for macro invocations.
+
+use hir::{Documentation, HasSource};
+use syntax::display::macro_label;
+use test_utils::mark;
+
+use crate::{
+    item::{CompletionItem, CompletionItemKind, CompletionKind},
+    render::RenderContext,
+};
+
+pub(crate) fn render_macro<'a>(
+    ctx: RenderContext<'a>,
+    name: String,
+    macro_: hir::MacroDef,
+) -> Option<CompletionItem> {
+    MacroRender::new(ctx, name, macro_).render()
+}
+
+#[derive(Debug)]
+struct MacroRender<'a> {
+    ctx: RenderContext<'a>,
+    name: String,
+    macro_: hir::MacroDef,
+    docs: Option<Documentation>,
+    bra: &'static str,
+    ket: &'static str,
+}
+
+impl<'a> MacroRender<'a> {
+    fn new(ctx: RenderContext<'a>, name: String, macro_: hir::MacroDef) -> MacroRender<'a> {
+        let docs = ctx.docs(macro_);
+        let docs_str = docs.as_ref().map_or("", |s| s.as_str());
+        let (bra, ket) = guess_macro_braces(&name, docs_str);
+
+        MacroRender { ctx, name, macro_, docs, bra, ket }
+    }
+
+    fn render(&self) -> Option<CompletionItem> {
+        // FIXME: Currently proc-macro do not have ast-node,
+        // such that it does not have source
+        if self.macro_.is_proc_macro() {
+            return None;
+        }
+
+        let mut builder =
+            CompletionItem::new(CompletionKind::Reference, self.ctx.source_range(), &self.label())
+                .kind(CompletionItemKind::Macro)
+                .set_documentation(self.docs.clone())
+                .set_deprecated(self.ctx.is_deprecated(self.macro_))
+                .detail(self.detail());
+
+        let needs_bang = self.needs_bang();
+        builder = match self.ctx.snippet_cap() {
+            Some(cap) if needs_bang => {
+                let snippet = self.snippet();
+                let lookup = self.lookup();
+                builder.insert_snippet(cap, snippet).lookup_by(lookup)
+            }
+            None if needs_bang => builder.insert_text(self.banged_name()),
+            _ => {
+                mark::hit!(dont_insert_macro_call_parens_unncessary);
+                builder.insert_text(&self.name)
+            }
+        };
+
+        Some(builder.build())
+    }
+
+    fn needs_bang(&self) -> bool {
+        self.ctx.completion.use_item_syntax.is_none() && !self.ctx.completion.is_macro_call
+    }
+
+    fn label(&self) -> String {
+        if self.needs_bang() && self.ctx.snippet_cap().is_some() {
+            format!("{}!{}…{}", self.name, self.bra, self.ket)
+        } else {
+            self.banged_name()
+        }
+    }
+
+    fn snippet(&self) -> String {
+        format!("{}!{}$0{}", self.name, self.bra, self.ket)
+    }
+
+    fn lookup(&self) -> String {
+        self.banged_name()
+    }
+
+    fn banged_name(&self) -> String {
+        format!("{}!", self.name)
+    }
+
+    fn detail(&self) -> String {
+        let ast_node = self.macro_.source(self.ctx.db()).value;
+        macro_label(&ast_node)
+    }
+}
+
+fn guess_macro_braces(macro_name: &str, docs: &str) -> (&'static str, &'static str) {
+    let mut votes = [0, 0, 0];
+    for (idx, s) in docs.match_indices(&macro_name) {
+        let (before, after) = (&docs[..idx], &docs[idx + s.len()..]);
+        // Ensure to match the full word
+        if after.starts_with('!')
+            && !before.ends_with(|c: char| c == '_' || c.is_ascii_alphanumeric())
+        {
+            // It may have spaces before the braces like `foo! {}`
+            match after[1..].chars().find(|&c| !c.is_whitespace()) {
+                Some('{') => votes[0] += 1,
+                Some('[') => votes[1] += 1,
+                Some('(') => votes[2] += 1,
+                _ => {}
+            }
+        }
+    }
+
+    // Insert a space before `{}`.
+    // We prefer the last one when some votes equal.
+    let (_vote, (bra, ket)) = votes
+        .iter()
+        .zip(&[(" {", "}"), ("[", "]"), ("(", ")")])
+        .max_by_key(|&(&vote, _)| vote)
+        .unwrap();
+    (*bra, *ket)
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::mark;
+
+    use crate::test_utils::check_edit;
+
+    #[test]
+    fn dont_insert_macro_call_parens_unncessary() {
+        mark::check!(dont_insert_macro_call_parens_unncessary);
+        check_edit(
+            "frobnicate!",
+            r#"
+//- /main.rs crate:main deps:foo
+use foo::<|>;
+//- /foo/lib.rs crate:foo
+#[macro_export]
+macro_rules frobnicate { () => () }
+"#,
+            r#"
+use foo::frobnicate;
+"#,
+        );
+
+        check_edit(
+            "frobnicate!",
+            r#"
+macro_rules frobnicate { () => () }
+fn main() { frob<|>!(); }
+"#,
+            r#"
+macro_rules frobnicate { () => () }
+fn main() { frobnicate!(); }
+"#,
+        );
+    }
+
+    #[test]
+    fn guesses_macro_braces() {
+        check_edit(
+            "vec!",
+            r#"
+/// Creates a [`Vec`] containing the arguments.
+///
+/// ```
+/// let v = vec![1, 2, 3];
+/// assert_eq!(v[0], 1);
+/// assert_eq!(v[1], 2);
+/// assert_eq!(v[2], 3);
+/// ```
+macro_rules! vec { () => {} }
+
+fn fn main() { v<|> }
+"#,
+            r#"
+/// Creates a [`Vec`] containing the arguments.
+///
+/// ```
+/// let v = vec![1, 2, 3];
+/// assert_eq!(v[0], 1);
+/// assert_eq!(v[1], 2);
+/// assert_eq!(v[2], 3);
+/// ```
+macro_rules! vec { () => {} }
+
+fn fn main() { vec![$0] }
+"#,
+        );
+
+        check_edit(
+            "foo!",
+            r#"
+/// Foo
+///
+/// Don't call `fooo!()` `fooo!()`, or `_foo![]` `_foo![]`,
+/// call as `let _=foo!  { hello world };`
+macro_rules! foo { () => {} }
+fn main() { <|> }
+"#,
+            r#"
+/// Foo
+///
+/// Don't call `fooo!()` `fooo!()`, or `_foo![]` `_foo![]`,
+/// call as `let _=foo!  { hello world };`
+macro_rules! foo { () => {} }
+fn main() { foo! {$0} }
+"#,
+        )
+    }
+}

crates/completion/src/render/type_alias.rs

@@ -0,0 +1,55 @@
+//! Renderer for type aliases.
+
+use hir::HasSource;
+use syntax::{
+    ast::{NameOwner, TypeAlias},
+    display::type_label,
+};
+
+use crate::{
+    item::{CompletionItem, CompletionItemKind, CompletionKind},
+    render::RenderContext,
+};
+
+pub(crate) fn render_type_alias<'a>(
+    ctx: RenderContext<'a>,
+    type_alias: hir::TypeAlias,
+) -> Option<CompletionItem> {
+    TypeAliasRender::new(ctx, type_alias).render()
+}
+
+#[derive(Debug)]
+struct TypeAliasRender<'a> {
+    ctx: RenderContext<'a>,
+    type_alias: hir::TypeAlias,
+    ast_node: TypeAlias,
+}
+
+impl<'a> TypeAliasRender<'a> {
+    fn new(ctx: RenderContext<'a>, type_alias: hir::TypeAlias) -> TypeAliasRender<'a> {
+        let ast_node = type_alias.source(ctx.db()).value;
+        TypeAliasRender { ctx, type_alias, ast_node }
+    }
+
+    fn render(self) -> Option<CompletionItem> {
+        let name = self.name()?;
+        let detail = self.detail();
+
+        let item = CompletionItem::new(CompletionKind::Reference, self.ctx.source_range(), name)
+            .kind(CompletionItemKind::TypeAlias)
+            .set_documentation(self.ctx.docs(self.type_alias))
+            .set_deprecated(self.ctx.is_deprecated(self.type_alias))
+            .detail(detail)
+            .build();
+
+        Some(item)
+    }
+
+    fn name(&self) -> Option<String> {
+        self.ast_node.name().map(|name| name.text().to_string())
+    }
+
+    fn detail(&self) -> String {
+        type_label(&self.ast_node)
+    }
+}