feat: filter out duplicate macro completions

closes #9303

13 files changed, 133 insertions, 95 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 7fea2137a0a..2373e79d82a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -460,6 +460,7 @@ dependencies = [
  "hir_def",
  "hir_expand",
  "hir_ty",
+ "indexmap",
  "itertools",
  "log",
  "once_cell",
diff --git a/crates/hir/Cargo.toml b/crates/hir/Cargo.toml
index 19249062015..b9561e6f9e2 100644
--- a/crates/hir/Cargo.toml
+++ b/crates/hir/Cargo.toml
@@ -16,6 +16,7 @@ arrayvec = "0.7"
 itertools = "0.10.0"
 smallvec = "1.4.0"
 once_cell = "1"
+indexmap = "1.7"
 
 stdx = { path = "../stdx", version = "0.0.0" }
 syntax = { path = "../syntax", version = "0.0.0" }
diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index cc320227f80..354fb276a51 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -923,31 +923,28 @@ impl<'a> SemanticsScope<'a> {
     }
 
     pub fn process_all_names(&self, f: &mut dyn FnMut(Name, ScopeDef)) {
-        let resolver = &self.resolver;
-
-        resolver.process_all_names(self.db.upcast(), &mut |name, def| {
-            let def = match def {
-                resolver::ScopeDef::PerNs(it) => {
-                    let items = ScopeDef::all_items(it);
-                    for item in items {
-                        f(name.clone(), item);
+        let scope = self.resolver.names_in_scope(self.db.upcast());
+        for (name, entries) in scope {
+            for entry in entries {
+                let def = match entry {
+                    resolver::ScopeDef::ModuleDef(it) => ScopeDef::ModuleDef(it.into()),
+                    resolver::ScopeDef::MacroDef(it) => ScopeDef::MacroDef(it.into()),
+                    resolver::ScopeDef::Unknown => ScopeDef::Unknown,
+                    resolver::ScopeDef::ImplSelfType(it) => ScopeDef::ImplSelfType(it.into()),
+                    resolver::ScopeDef::AdtSelfType(it) => ScopeDef::AdtSelfType(it.into()),
+                    resolver::ScopeDef::GenericParam(id) => ScopeDef::GenericParam(id.into()),
+                    resolver::ScopeDef::Local(pat_id) => {
+                        let parent = self.resolver.body_owner().unwrap();
+                        ScopeDef::Local(Local { parent, pat_id })
                     }
-                    return;
-                }
-                resolver::ScopeDef::ImplSelfType(it) => ScopeDef::ImplSelfType(it.into()),
-                resolver::ScopeDef::AdtSelfType(it) => ScopeDef::AdtSelfType(it.into()),
-                resolver::ScopeDef::GenericParam(id) => ScopeDef::GenericParam(id.into()),
-                resolver::ScopeDef::Local(pat_id) => {
-                    let parent = resolver.body_owner().unwrap();
-                    ScopeDef::Local(Local { parent, pat_id })
-                }
-                resolver::ScopeDef::Label(label_id) => {
-                    let parent = resolver.body_owner().unwrap();
-                    ScopeDef::Label(Label { parent, label_id })
-                }
-            };
-            f(name, def)
-        })
+                    resolver::ScopeDef::Label(label_id) => {
+                        let parent = self.resolver.body_owner().unwrap();
+                        ScopeDef::Label(Label { parent, label_id })
+                    }
+                };
+                f(name.clone(), def)
+            }
+        }
     }
 
     /// Resolve a path as-if it was written at the given scope. This is
diff --git a/crates/hir_def/src/resolver.rs b/crates/hir_def/src/resolver.rs
index cd1a6c6864f..0cf28acf7ff 100644
--- a/crates/hir_def/src/resolver.rs
+++ b/crates/hir_def/src/resolver.rs
@@ -6,7 +6,9 @@ use hir_expand::{
     name::{name, Name},
     MacroDefId,
 };
+use indexmap::IndexMap;
 use rustc_hash::FxHashSet;
+use smallvec::SmallVec;
 
 use crate::{
     body::scope::{ExprScopes, ScopeId},
@@ -348,10 +350,50 @@ impl Resolver {
         item_map.resolve_path(db, module, path, BuiltinShadowMode::Other).0.take_macros()
     }
 
-    pub fn process_all_names(&self, db: &dyn DefDatabase, f: &mut dyn FnMut(Name, ScopeDef)) {
+    /// Returns a set of names available in the current scope.
+    ///
+    /// Note that this is a somewhat fuzzy concept -- internally, the compiler
+    /// doesn't necessary follow a strict scoping discipline. Rathe, it just
+    /// tells for each ident what it resolves to.
+    ///
+    /// A good example is something like `str::from_utf8`. From scopes point of
+    /// view, this code is erroneous -- both `str` module and `str` type occupy
+    /// the same type namespace.
+    ///
+    /// We don't try to model that super-correctly -- this functionality is
+    /// primarily exposed for completions.
+    ///
+    /// Note that in Rust one name can be bound to several items:
+    ///
+    /// ```
+    /// macro_rules! t { () => (()) }
+    /// type t = t!();
+    /// const t: t = t!()
+    /// ```
+    ///
+    /// That's why we return a multimap.
+    ///
+    /// The shadowing is accounted for: in
+    ///
+    /// ```
+    /// let x = 92;
+    /// {
+    ///     let x = 92;
+    ///     $0
+    /// }
+    /// ```
+    ///
+    /// there will be only one entry for `x` in the result.
+    ///
+    /// The result is ordered *roughly* from the innermost scope to the
+    /// outermost: when the name is introduced in two namespaces in two scopes,
+    /// we use the position of the first scope.
+    pub fn names_in_scope(&self, db: &dyn DefDatabase) -> IndexMap<Name, SmallVec<[ScopeDef; 1]>> {
+        let mut res = ScopeNames::default();
         for scope in self.scopes() {
-            scope.process_names(db, f);
+            scope.process_names(db, &mut res);
         }
+        res.map
     }
 
     pub fn traits_in_scope(&self, db: &dyn DefDatabase) -> FxHashSet<TraitId> {
@@ -434,8 +476,11 @@ impl Resolver {
     }
 }
 
+#[derive(Debug, PartialEq, Eq)]
 pub enum ScopeDef {
-    PerNs(PerNs),
+    ModuleDef(ModuleDefId),
+    MacroDef(MacroDefId),
+    Unknown,
     ImplSelfType(ImplId),
     AdtSelfType(AdtId),
     GenericParam(GenericParamId),
@@ -444,8 +489,7 @@ pub enum ScopeDef {
 }
 
 impl Scope {
-    fn process_names(&self, db: &dyn DefDatabase, f: &mut dyn FnMut(Name, ScopeDef)) {
-        let mut seen = FxHashSet::default();
+    fn process_names(&self, db: &dyn DefDatabase, acc: &mut ScopeNames) {
         match self {
             Scope::ModuleScope(m) => {
                 // FIXME: should we provide `self` here?
@@ -456,58 +500,53 @@ impl Scope {
                 //     }),
                 // );
                 m.def_map[m.module_id].scope.entries().for_each(|(name, def)| {
-                    f(name.clone(), ScopeDef::PerNs(def));
+                    acc.add_per_ns(name, def);
                 });
-                m.def_map[m.module_id].scope.legacy_macros().for_each(|(name, macro_)| {
-                    let scope = PerNs::macros(macro_, Visibility::Public);
-                    seen.insert((name.clone(), scope));
-                    f(name.clone(), ScopeDef::PerNs(scope));
+                m.def_map[m.module_id].scope.legacy_macros().for_each(|(name, mac)| {
+                    acc.add(name, ScopeDef::MacroDef(mac));
                 });
                 m.def_map.extern_prelude().for_each(|(name, &def)| {
-                    f(name.clone(), ScopeDef::PerNs(PerNs::types(def, Visibility::Public)));
+                    acc.add(name, ScopeDef::ModuleDef(def));
                 });
                 BUILTIN_SCOPE.iter().for_each(|(name, &def)| {
-                    f(name.clone(), ScopeDef::PerNs(def));
+                    acc.add_per_ns(name, def);
                 });
                 if let Some(prelude) = m.def_map.prelude() {
                     let prelude_def_map = prelude.def_map(db);
-                    prelude_def_map[prelude.local_id].scope.entries().for_each(|(name, def)| {
-                        let seen_tuple = (name.clone(), def);
-                        if !seen.contains(&seen_tuple) {
-                            f(seen_tuple.0, ScopeDef::PerNs(def));
-                        }
-                    });
+                    for (name, def) in prelude_def_map[prelude.local_id].scope.entries() {
+                        acc.add_per_ns(name, def)
+                    }
                 }
             }
             Scope::GenericParams { params, def: parent } => {
                 let parent = *parent;
                 for (local_id, param) in params.types.iter() {
-                    if let Some(ref name) = param.name {
+                    if let Some(name) = &param.name {
                         let id = TypeParamId { parent, local_id };
-                        f(name.clone(), ScopeDef::GenericParam(id.into()))
+                        acc.add(name, ScopeDef::GenericParam(id.into()))
                     }
                 }
                 for (local_id, param) in params.consts.iter() {
                     let id = ConstParamId { parent, local_id };
-                    f(param.name.clone(), ScopeDef::GenericParam(id.into()))
+                    acc.add(&param.name, ScopeDef::GenericParam(id.into()))
                 }
                 for (local_id, param) in params.lifetimes.iter() {
                     let id = LifetimeParamId { parent, local_id };
-                    f(param.name.clone(), ScopeDef::GenericParam(id.into()))
+                    acc.add(&param.name, ScopeDef::GenericParam(id.into()))
                 }
             }
             Scope::ImplDefScope(i) => {
-                f(name![Self], ScopeDef::ImplSelfType(*i));
+                acc.add(&name![Self], ScopeDef::ImplSelfType(*i));
             }
             Scope::AdtScope(i) => {
-                f(name![Self], ScopeDef::AdtSelfType(*i));
+                acc.add(&name![Self], ScopeDef::AdtSelfType(*i));
             }
             Scope::ExprScope(scope) => {
                 if let Some((label, name)) = scope.expr_scopes.label(scope.scope_id) {
-                    f(name, ScopeDef::Label(label))
+                    acc.add(&name, ScopeDef::Label(label))
                 }
                 scope.expr_scopes.entries(scope.scope_id).iter().for_each(|e| {
-                    f(e.name().clone(), ScopeDef::Local(e.pat()));
+                    acc.add_local(e.name(), e.pat());
                 });
             }
         }
@@ -651,6 +690,47 @@ fn to_type_ns(per_ns: PerNs) -> Option<TypeNs> {
     Some(res)
 }
 
+#[derive(Default)]
+struct ScopeNames {
+    map: IndexMap<Name, SmallVec<[ScopeDef; 1]>>,
+}
+
+impl ScopeNames {
+    fn add(&mut self, name: &Name, def: ScopeDef) {
+        let set = self.map.entry(name.clone()).or_default();
+        if !set.contains(&def) {
+            set.push(def)
+        }
+    }
+    fn add_per_ns(&mut self, name: &Name, def: PerNs) {
+        if let Some(ty) = &def.types {
+            self.add(name, ScopeDef::ModuleDef(ty.0))
+        }
+        if let Some(val) = &def.values {
+            self.add(name, ScopeDef::ModuleDef(val.0))
+        }
+        if let Some(mac) = &def.macros {
+            self.add(name, ScopeDef::MacroDef(mac.0))
+        }
+        if def.is_none() {
+            self.add(name, ScopeDef::Unknown)
+        }
+    }
+    fn add_local(&mut self, name: &Name, pat: PatId) {
+        let set = self.map.entry(name.clone()).or_default();
+        // XXX: hack, account for local (and only local) shadowing.
+        //
+        // This should be somewhat more principled and take namespaces into
+        // accounts, but, alas, scoping rules are a hoax. `str` type and `str`
+        // module can be both available in the same scope.
+        if set.iter().any(|it| matches!(it, &ScopeDef::Local(_))) {
+            cov_mark::hit!(shadowing_shows_single_completion);
+            return;
+        }
+        set.push(ScopeDef::Local(pat))
+    }
+}
+
 pub trait HasResolver: Copy {
     /// Builds a resolver for type references inside this def.
     fn resolver(self, db: &dyn DefDatabase) -> Resolver;
diff --git a/crates/ide_completion/src/completions/unqualified_path.rs b/crates/ide_completion/src/completions/unqualified_path.rs
index 0af282d83db..d81cb5391cb 100644
--- a/crates/ide_completion/src/completions/unqualified_path.rs
+++ b/crates/ide_completion/src/completions/unqualified_path.rs
@@ -304,25 +304,4 @@ pub mod prelude {
             "#]],
         );
     }
-
-    #[test]
-    fn local_variable_shadowing() {
-        // FIXME: this isn't actually correct, should emit `x` only once.
-        check(
-            r#"
-fn main() {
-    let x = 92;
-    {
-        let x = 92;
-        x$0;
-    }
-}
-"#,
-            expect![[r#"
-                lc x      i32
-                lc x      i32
-                fn main() fn()
-            "#]],
-        );
-    }
 }
diff --git a/crates/ide_completion/src/render.rs b/crates/ide_completion/src/render.rs
index 6585b1cc8ae..23be915bbc9 100644
--- a/crates/ide_completion/src/render.rs
+++ b/crates/ide_completion/src/render.rs
@@ -1348,10 +1348,10 @@ fn foo() {
                 lc foo [type+local]
                 ev Foo::A(…) [type_could_unify]
                 ev Foo::B [type_could_unify]
+                fn foo() []
                 en Foo []
                 fn baz() []
                 fn bar() []
-                fn foo() []
             "#]],
         );
     }
diff --git a/crates/ide_completion/src/tests/expression.rs b/crates/ide_completion/src/tests/expression.rs
index cf22fb20ab1..5c8dccc7803 100644
--- a/crates/ide_completion/src/tests/expression.rs
+++ b/crates/ide_completion/src/tests/expression.rs
@@ -118,7 +118,6 @@ impl Unit {
             un Union
             ev TupleV(…)    (u32)
             ct CONST
-            ma makro!(…)    #[macro_export] macro_rules! makro
             me self.foo()   fn(self)
         "##]],
     );
@@ -155,6 +154,8 @@ impl Unit {
 
 #[test]
 fn shadowing_shows_single_completion() {
+    cov_mark::check!(shadowing_shows_single_completion);
+
     check_empty(
         r#"
 fn foo() {
@@ -165,7 +166,6 @@ fn foo() {
     }
 }
 "#,
-        // FIXME: should be only one bar here
         expect![[r#"
             kw unsafe
             kw match
@@ -182,7 +182,6 @@ fn foo() {
             kw super
             kw crate
             lc bar       i32
-            lc bar       i32
             fn foo()     fn()
             bt u32
         "#]],
diff --git a/crates/ide_completion/src/tests/item.rs b/crates/ide_completion/src/tests/item.rs
index ad87bdc7513..aa298fa0bf8 100644
--- a/crates/ide_completion/src/tests/item.rs
+++ b/crates/ide_completion/src/tests/item.rs
@@ -29,7 +29,6 @@ impl Tra$0
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…) #[macro_export] macro_rules! makro
             bt u32
         "##]],
     )
@@ -53,7 +52,6 @@ impl Trait for Str$0
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…) #[macro_export] macro_rules! makro
             bt u32
         "##]],
     )
diff --git a/crates/ide_completion/src/tests/item_list.rs b/crates/ide_completion/src/tests/item_list.rs
index bd8df49e41e..f355d37afc2 100644
--- a/crates/ide_completion/src/tests/item_list.rs
+++ b/crates/ide_completion/src/tests/item_list.rs
@@ -67,7 +67,6 @@ fn in_source_file_item_list() {
             kw crate
             md module
             ma makro!(…)           #[macro_export] macro_rules! makro
-            ma makro!(…)           #[macro_export] macro_rules! makro
         "##]],
     )
 }
@@ -172,7 +171,6 @@ fn in_impl_assoc_item_list() {
             kw crate
             md module
             ma makro!(…)  #[macro_export] macro_rules! makro
-            ma makro!(…)  #[macro_export] macro_rules! makro
         "##]],
     )
 }
@@ -206,7 +204,6 @@ fn in_trait_assoc_item_list() {
             kw crate
             md module
             ma makro!(…) #[macro_export] macro_rules! makro
-            ma makro!(…) #[macro_export] macro_rules! makro
         "##]],
     );
 }
@@ -243,7 +240,6 @@ impl Test for () {
             kw crate
             md module
             ma makro!(…)  #[macro_export] macro_rules! makro
-            ma makro!(…)  #[macro_export] macro_rules! makro
         "##]],
     );
 }
diff --git a/crates/ide_completion/src/tests/pattern.rs b/crates/ide_completion/src/tests/pattern.rs
index 5791921e448..10647e490ee 100644
--- a/crates/ide_completion/src/tests/pattern.rs
+++ b/crates/ide_completion/src/tests/pattern.rs
@@ -122,7 +122,6 @@ fn foo() {
             bn TupleV    TupleV($1)$0
             ev TupleV
             ct CONST
-            ma makro!(…) #[macro_export] macro_rules! makro
         "##]],
     );
 }
@@ -143,7 +142,6 @@ fn foo() {
             st Tuple
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
-            ma makro!(…) #[macro_export] macro_rules! makro
         "##]],
     );
 }
@@ -163,7 +161,6 @@ fn foo(a$0) {
             st Tuple
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
-            ma makro!(…) #[macro_export] macro_rules! makro
         "##]],
     );
 }
diff --git a/crates/ide_completion/src/tests/predicate.rs b/crates/ide_completion/src/tests/predicate.rs
index d43e4b50b13..163080307d7 100644
--- a/crates/ide_completion/src/tests/predicate.rs
+++ b/crates/ide_completion/src/tests/predicate.rs
@@ -28,7 +28,6 @@ struct Foo<'lt, T, const C: usize> where $0 {}
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…) #[macro_export] macro_rules! makro
             bt u32
         "##]],
     );
@@ -47,7 +46,6 @@ struct Foo<'lt, T, const C: usize> where T: $0 {}
             tt Trait
             md module
             ma makro!(…) #[macro_export] macro_rules! makro
-            ma makro!(…) #[macro_export] macro_rules! makro
         "##]],
     );
 }
@@ -67,7 +65,6 @@ struct Foo<'lt, T, const C: usize> where 'lt: $0 {}
             tt Trait
             md module
             ma makro!(…) #[macro_export] macro_rules! makro
-            ma makro!(…) #[macro_export] macro_rules! makro
         "##]],
     );
 }
@@ -85,7 +82,6 @@ struct Foo<'lt, T, const C: usize> where for<'a> T: $0 {}
             tt Trait
             md module
             ma makro!(…) #[macro_export] macro_rules! makro
-            ma makro!(…) #[macro_export] macro_rules! makro
         "##]],
     );
 }
@@ -109,7 +105,6 @@ struct Foo<'lt, T, const C: usize> where for<'a> $0 {}
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…) #[macro_export] macro_rules! makro
             bt u32
         "##]],
     );
@@ -136,7 +131,6 @@ impl Record {
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…) #[macro_export] macro_rules! makro
             bt u32
         "##]],
     );
diff --git a/crates/ide_completion/src/tests/type_pos.rs b/crates/ide_completion/src/tests/type_pos.rs
index 88146357ca7..b6cf8945e23 100644
--- a/crates/ide_completion/src/tests/type_pos.rs
+++ b/crates/ide_completion/src/tests/type_pos.rs
@@ -31,7 +31,6 @@ struct Foo<'lt, T, const C: usize> {
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…) #[macro_export] macro_rules! makro
             bt u32
         "##]],
     )
@@ -60,7 +59,6 @@ struct Foo<'lt, T, const C: usize>(f$0);
             st Unit
             ma makro!(…)  #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…)  #[macro_export] macro_rules! makro
             bt u32
         "##]],
     )
@@ -85,7 +83,6 @@ fn x<'lt, T, const C: usize>() -> $0
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…) #[macro_export] macro_rules! makro
             bt u32
         "##]],
     );
@@ -113,7 +110,6 @@ fn foo<'lt, T, const C: usize>() {
             st Unit
             ma makro!(…) #[macro_export] macro_rules! makro
             un Union
-            ma makro!(…) #[macro_export] macro_rules! makro
             bt u32
         "##]],
     );
@@ -164,7 +160,6 @@ fn foo<'lt, T: Trait2<$0>, const CONST_PARAM: usize>(_: T) {}
             tt Trait2
             un Union
             ct CONST
-            ma makro!(…)          #[macro_export] macro_rules! makro
             bt u32
         "##]],
     );
diff --git a/docs/dev/style.md b/docs/dev/style.md
index d5340e2b8e3..3edbaf89d8c 100644
--- a/docs/dev/style.md
+++ b/docs/dev/style.md
@@ -839,6 +839,7 @@ crate  -> krate
 enum   -> enum_
 fn     -> func
 impl   -> imp
+macro  -> mac
 mod    -> module
 struct -> strukt
 trait  -> trait_