From 9fe10a96069ea0f617ff86049bb50922b5424fae Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Thu, 1 Apr 2021 21:52:07 +0200
Subject: Resolve associated types with type anchors

---
 crates/hir/src/source_analyzer.rs | 29 +++++++++++++++++++----------
 crates/hir_ty/src/lower.rs        |  2 +-
 crates/ide/src/hover.rs           | 23 ++++++++++++++++++++++-
 3 files changed, 42 insertions(+), 12 deletions(-)

(limited to 'crates')

diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
index 8423dd101..8e9ea0a03 100644
--- a/crates/hir/src/source_analyzer.rs
+++ b/crates/hir/src/source_analyzer.rs
@@ -20,7 +20,7 @@ use hir_def::{
 use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
 use hir_ty::{
     diagnostics::{record_literal_missing_fields, record_pattern_missing_fields},
-    InferenceResult, Substitution,
+    InferenceResult, Substitution, TyLoweringContext,
 };
 use syntax::{
     ast::{self, AstNode},
@@ -466,7 +466,20 @@ fn resolve_hir_path_(
     prefer_value_ns: bool,
 ) -> Option<PathResolution> {
     let types = || {
-        let (ty, remaining) = resolver.resolve_path_in_type_ns(db.upcast(), path.mod_path())?;
+        let (ty, unresolved) = match path.type_anchor() {
+            Some(type_ref) => {
+                let (_, res) = TyLoweringContext::new(db, resolver).lower_ty_ext(type_ref);
+                res.map(|ty_ns| (ty_ns, path.segments().first()))
+            }
+            None => {
+                let (ty, remaining) =
+                    resolver.resolve_path_in_type_ns(db.upcast(), path.mod_path())?;
+                match remaining {
+                    Some(remaining) if remaining > 1 => None,
+                    _ => Some((ty, path.segments().get(1))),
+                }
+            }
+        }?;
         let res = match ty {
             TypeNs::SelfType(it) => PathResolution::SelfType(it.into()),
             TypeNs::GenericParam(id) => PathResolution::TypeParam(TypeParam { id }),
@@ -478,18 +491,14 @@ fn resolve_hir_path_(
             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| {
+        match unresolved {
+            Some(unresolved) => 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,
+                .map(PathResolution::Def),
             None => Some(res),
         }
     };
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index afbfa12d5..14f34d73c 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -146,7 +146,7 @@ impl<'a> TyLoweringContext<'a> {
         self.lower_ty_ext(type_ref).0
     }
 
-    fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
+    pub fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
         let mut res = None;
         let ty = match type_ref {
             TypeRef::Never => TyKind::Never.intern(&Interner),
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index 8f98056c1..28e2e17dc 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -3841,6 +3841,27 @@ fn foo() {}
             r#"
 fn foo<T: A>() where T::Assoc$0: {}
 
+trait A {
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
+            "#]],
+        );
+        check(
+            r#"
+fn foo<T: A>() {
+    let _: <T>::Assoc$0;
+}
+
 trait A {
     type Assoc;
 }"#,
@@ -3874,6 +3895,6 @@ trait A where
                 type Assoc
                 ```
             "#]],
-        )
+        );
     }
 }
-- 
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