From 41c7448e1242de8fadf7c46efd3171368b5ff92e Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Tue, 30 Mar 2021 02:08:33 +0200
Subject: Accurately classify assoc. types in paths

---
 crates/ide/src/goto_definition.rs | 15 ++++++++++++++
 crates/ide_db/src/defs.rs         | 41 ++++++++++++++++++++++-----------------
 2 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/crates/ide/src/goto_definition.rs b/crates/ide/src/goto_definition.rs
index a2c97061f..c6556c487 100644
--- a/crates/ide/src/goto_definition.rs
+++ b/crates/ide/src/goto_definition.rs
@@ -917,6 +917,21 @@ fn f() -> impl Iterator<Item$0 = u8> {}
         );
     }
 
+    #[test]
+    #[should_panic = "unresolved reference"]
+    fn unknown_assoc_ty() {
+        check(
+            r#"
+trait Iterator {
+    type Item;
+       //^^^^
+}
+
+fn f() -> impl Iterator<Invalid$0 = u8> {}
+            "#,
+        )
+    }
+
     #[test]
     fn goto_def_for_assoc_ty_in_path_multiple() {
         check(
diff --git a/crates/ide_db/src/defs.rs b/crates/ide_db/src/defs.rs
index 0d9808d24..de0dc2a40 100644
--- a/crates/ide_db/src/defs.rs
+++ b/crates/ide_db/src/defs.rs
@@ -330,25 +330,30 @@ impl NameRefClass {
             }
         }
 
-        if ast::AssocTypeArg::cast(parent.clone()).is_some() {
-            // `Trait<Assoc = Ty>`
-            //        ^^^^^
-            let path = name_ref.syntax().ancestors().find_map(ast::Path::cast)?;
-            let resolved = sema.resolve_path(&path)?;
-            if let PathResolution::Def(ModuleDef::Trait(tr)) = resolved {
-                if let Some(ty) = tr
-                    .items(sema.db)
-                    .iter()
-                    .filter_map(|assoc| match assoc {
-                        hir::AssocItem::TypeAlias(it) => Some(*it),
-                        _ => None,
-                    })
-                    .find(|alias| &alias.name(sema.db).to_string() == &name_ref.text())
-                {
-                    return Some(NameRefClass::Definition(Definition::ModuleDef(
-                        ModuleDef::TypeAlias(ty),
-                    )));
+        if let Some(assoc_type_arg) = ast::AssocTypeArg::cast(parent.clone()) {
+            if assoc_type_arg.name_ref().as_ref() == Some(name_ref) {
+                // `Trait<Assoc = Ty>`
+                //        ^^^^^
+                let path = name_ref.syntax().ancestors().find_map(ast::Path::cast)?;
+                let resolved = sema.resolve_path(&path)?;
+                if let PathResolution::Def(ModuleDef::Trait(tr)) = resolved {
+                    // FIXME: resolve in supertraits
+                    if let Some(ty) = tr
+                        .items(sema.db)
+                        .iter()
+                        .filter_map(|assoc| match assoc {
+                            hir::AssocItem::TypeAlias(it) => Some(*it),
+                            _ => None,
+                        })
+                        .find(|alias| &alias.name(sema.db).to_string() == &name_ref.text())
+                    {
+                        return Some(NameRefClass::Definition(Definition::ModuleDef(
+                            ModuleDef::TypeAlias(ty),
+                        )));
+                    }
                 }
+
+                return None;
             }
         }
 
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