fix(completion): derive source scope from syntax node to be transformed

crates/hir/src/semantics.rs

@@ -483,10 +483,6 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         self.imp.scope_at_offset(node, offset)
     }
 
-    pub fn scope_for_def(&self, def: Trait) -> SemanticsScope<'db> {
-        self.imp.scope_for_def(def)
-    }
-
     pub fn assert_contains_node(&self, node: &SyntaxNode) {
         self.imp.assert_contains_node(node)
     }
@@ -1307,12 +1303,6 @@ impl<'db> SemanticsImpl<'db> {
         )
     }
 
-    fn scope_for_def(&self, def: Trait) -> SemanticsScope<'db> {
-        let file_id = self.db.lookup_intern_trait(def.id).id.file_id();
-        let resolver = def.id.resolver(self.db.upcast());
-        SemanticsScope { db: self.db, file_id, resolver }
-    }
-
     fn source<Def: HasSource>(&self, def: Def) -> Option<InFile<Def::Ast>>
     where
         Def::Ast: AstNode,

crates/ide-completion/src/completions/item_list/trait_impl.rs

@@ -227,9 +227,8 @@ fn get_transformed_assoc_item(
     assoc_item: ast::AssocItem,
     impl_def: hir::Impl,
 ) -> Option<ast::AssocItem> {
-    let assoc_item = assoc_item.clone_for_update();
     let trait_ = impl_def.trait_(ctx.db)?;
-    let source_scope = &ctx.sema.scope_for_def(trait_);
+    let source_scope = &ctx.sema.scope(assoc_item.syntax())?;
     let target_scope = &ctx.sema.scope(ctx.sema.source(impl_def)?.syntax().value)?;
     let transform = PathTransform::trait_impl(
         target_scope,
@@ -238,6 +237,9 @@ fn get_transformed_assoc_item(
         ctx.sema.source(impl_def)?.value,
     );
 
+    let assoc_item = assoc_item.clone_for_update();
+    // FIXME: Paths in nested macros are not handled well. See
+    // `macro_generated_assoc_item2` test.
     transform.apply(assoc_item.syntax());
     assoc_item.remove_attrs_and_docs();
     Some(assoc_item)
@@ -1193,6 +1195,81 @@ impl Foo for Test {
         );
     }
 
+    #[test]
+    fn macro_generated_assoc_item() {
+        check_edit(
+            "fn method",
+            r#"
+macro_rules! ty { () => { i32 } }
+trait SomeTrait { type Output; }
+impl SomeTrait for i32 { type Output = i64; }
+macro_rules! define_method {
+    () => {
+        fn method(&mut self, params: <ty!() as SomeTrait>::Output);
+    };
+}
+trait AnotherTrait { define_method!(); }
+impl AnotherTrait for () {
+    $0
+}
+"#,
+            r#"
+macro_rules! ty { () => { i32 } }
+trait SomeTrait { type Output; }
+impl SomeTrait for i32 { type Output = i64; }
+macro_rules! define_method {
+    () => {
+        fn method(&mut self, params: <ty!() as SomeTrait>::Output);
+    };
+}
+trait AnotherTrait { define_method!(); }
+impl AnotherTrait for () {
+    fn method(&mut self,params: <ty!()as SomeTrait>::Output) {
+    $0
+}
+}
+"#,
+        );
+    }
+
+    // FIXME: `T` in `ty!(T)` should be replaced by `PathTransform`.
+    #[test]
+    fn macro_generated_assoc_item2() {
+        check_edit(
+            "fn method",
+            r#"
+macro_rules! ty { ($me:ty) => { $me } }
+trait SomeTrait { type Output; }
+impl SomeTrait for i32 { type Output = i64; }
+macro_rules! define_method {
+    ($t:ty) => {
+        fn method(&mut self, params: <ty!($t) as SomeTrait>::Output);
+    };
+}
+trait AnotherTrait<T: SomeTrait> { define_method!(T); }
+impl AnotherTrait<i32> for () {
+    $0
+}
+"#,
+            r#"
+macro_rules! ty { ($me:ty) => { $me } }
+trait SomeTrait { type Output; }
+impl SomeTrait for i32 { type Output = i64; }
+macro_rules! define_method {
+    ($t:ty) => {
+        fn method(&mut self, params: <ty!($t) as SomeTrait>::Output);
+    };
+}
+trait AnotherTrait<T: SomeTrait> { define_method!(T); }
+impl AnotherTrait<i32> for () {
+    fn method(&mut self,params: <ty!(T)as SomeTrait>::Output) {
+    $0
+}
+}
+"#,
+        );
+    }
+
     #[test]
     fn includes_gat_generics() {
         check_edit(