From 444f6caababc3335b1ed51d08eeedac106fd8077 Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Thu, 1 Apr 2021 18:01:18 +0200
Subject: Resolve associated types

---
 crates/hir/src/semantics.rs                        |  6 ++--
 crates/hir/src/source_analyzer.rs                  | 19 ++++++++--
 crates/ide/src/hover.rs                            | 42 ++++++++++++++++++++++
 .../src/completions/qualified_path.rs              |  2 +-
 4 files changed, 64 insertions(+), 5 deletions(-)

(limited to 'crates')

diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index d3caeef4e..3bf722d2a 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -76,9 +76,11 @@ impl PathResolution {
     pub fn assoc_type_shorthand_candidates<R>(
         &self,
         db: &dyn HirDatabase,
-        mut cb: impl FnMut(TypeAlias) -> Option<R>,
+        mut cb: impl FnMut(&Name, TypeAlias) -> Option<R>,
     ) -> Option<R> {
-        associated_type_shorthand_candidates(db, self.in_type_ns()?, |_, _, id| cb(id.into()))
+        associated_type_shorthand_candidates(db, self.in_type_ns()?, |name, _, id| {
+            cb(name, id.into())
+        })
     }
 }
 
diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
index 37d162b32..8423dd101 100644
--- a/crates/hir/src/source_analyzer.rs
+++ b/crates/hir/src/source_analyzer.rs
@@ -466,7 +466,8 @@ fn resolve_hir_path_(
     prefer_value_ns: bool,
 ) -> Option<PathResolution> {
     let types = || {
-        resolver.resolve_path_in_type_ns_fully(db.upcast(), path.mod_path()).map(|ty| match ty {
+        let (ty, remaining) = resolver.resolve_path_in_type_ns(db.upcast(), path.mod_path())?;
+        let res = match ty {
             TypeNs::SelfType(it) => PathResolution::SelfType(it.into()),
             TypeNs::GenericParam(id) => PathResolution::TypeParam(TypeParam { id }),
             TypeNs::AdtSelfType(it) | TypeNs::AdtId(it) => {
@@ -476,7 +477,21 @@ fn resolve_hir_path_(
             TypeNs::TypeAliasId(it) => PathResolution::Def(TypeAlias::from(it).into()),
             TypeNs::BuiltinType(it) => PathResolution::Def(BuiltinType::from(it).into()),
             TypeNs::TraitId(it) => PathResolution::Def(Trait::from(it).into()),
-        })
+        };
+        match remaining {
+            Some(1) => {
+                let unresolved = path.segments().get(1)?;
+                res.assoc_type_shorthand_candidates(db, |name, alias| {
+                    (name == unresolved.name).then(|| alias)
+                })
+                .map(TypeAlias::from)
+                .map(Into::into)
+                .map(PathResolution::Def)
+            }
+            // ambiguous
+            Some(_) => None,
+            None => Some(res),
+        }
     };
 
     let body_owner = resolver.body_owner();
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index 5f9edb476..8f98056c1 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -3834,4 +3834,46 @@ fn foo() {}
             "#]],
         );
     }
+
+    #[test]
+    fn hover_generic_assoc() {
+        check(
+            r#"
+fn foo<T: A>() where T::Assoc$0: {}
+
+trait A {
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
+            "#]],
+        );
+        check(
+            r#"
+trait A where
+    Self::Assoc$0: ,
+{
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
+            "#]],
+        )
+    }
 }
diff --git a/crates/ide_completion/src/completions/qualified_path.rs b/crates/ide_completion/src/completions/qualified_path.rs
index 1891eb5b3..969249df6 100644
--- a/crates/ide_completion/src/completions/qualified_path.rs
+++ b/crates/ide_completion/src/completions/qualified_path.rs
@@ -24,7 +24,7 @@ pub(crate) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
     };
 
     // Add associated types on type parameters and `Self`.
-    resolution.assoc_type_shorthand_candidates(ctx.db, |alias| {
+    resolution.assoc_type_shorthand_candidates(ctx.db, |_, alias| {
         acc.add_type_alias(ctx, alias);
         None::<()>
     });
-- 
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