3 files changed, 43 insertions, 5 deletions

diff --git a/crates/ra_hir/src/ty/method_resolution.rs b/crates/ra_hir/src/ty/method_resolution.rs
index 8d1076774..94b757af2 100644
--- a/crates/ra_hir/src/ty/method_resolution.rs
+++ b/crates/ra_hir/src/ty/method_resolution.rs
@@ -118,11 +118,13 @@ impl Ty {
     // TODO: cache this as a query?
     // - if so, what signature? (TyFingerprint, Name)?
     // - or maybe cache all names and def_ids of methods per fingerprint?
-    pub fn lookup_method(self, db: &impl HirDatabase, name: &Name) -> Option<Function> {
-        self.iterate_methods(db, |f| {
+    /// Look up the method with the given name, returning the actual autoderefed
+    /// receiver type (but without autoref applied yet).
+    pub fn lookup_method(self, db: &impl HirDatabase, name: &Name) -> Option<(Ty, Function)> {
+        self.iterate_methods(db, |ty, f| {
             let sig = f.signature(db);
             if sig.name() == name && sig.has_self_param() {
-                Some(f)
+                Some((ty.clone(), f))
             } else {
                 None
             }
@@ -134,7 +136,7 @@ impl Ty {
     pub fn iterate_methods<T>(
         self,
         db: &impl HirDatabase,
-        mut callback: impl FnMut(Function) -> Option<T>,
+        mut callback: impl FnMut(&Ty, Function) -> Option<T>,
     ) -> Option<T> {
         // For method calls, rust first does any number of autoderef, and then one
         // autoref (i.e. when the method takes &self or &mut self). We just ignore
@@ -156,7 +158,7 @@ impl Ty {
                 for item in impl_block.items(db) {
                     match item {
                         ImplItem::Method(f) => {
-                            if let Some(result) = callback(f) {
+                            if let Some(result) = callback(&derefed_ty, f) {
                                 return Some(result);
                             }
                         }
diff --git a/crates/ra_hir/src/ty/snapshots/tests__infer_impl_generics_with_autoderef.snap b/crates/ra_hir/src/ty/snapshots/tests__infer_impl_generics_with_autoderef.snap
new file mode 100644
index 000000000..f609eaf7c
--- /dev/null
+++ b/crates/ra_hir/src/ty/snapshots/tests__infer_impl_generics_with_autoderef.snap
@@ -0,0 +1,16 @@
+---
+created: "2019-02-17T13:35:06.385679926Z"
+creator: [email protected]
+source: crates/ra_hir/src/ty/tests.rs
+expression: "&result"
+---
+[78; 82) 'self': &Option<T>
+[98; 100) '{}': ()
+[111; 112) 'o': Option<u32>
+[127; 165) '{     ...f(); }': ()
+[133; 146) '(&o).as_ref()': Option<&u32>
+[134; 136) '&o': &Option<u32>
+[135; 136) 'o': Option<u32>
+[152; 153) 'o': Option<u32>
+[152; 162) 'o.as_ref()': Option<&u32>
+
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index 1eca68dc5..5eb9c4f5b 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -539,6 +539,26 @@ fn test() -> i128 {
 }
 
 #[test]
+fn infer_impl_generics_with_autoderef() {
+    check_inference(
+        "infer_impl_generics_with_autoderef",
+        r#"
+enum Option<T> {
+    Some(T),
+    None,
+}
+impl<T> Option<T> {
+    fn as_ref(&self) -> Option<&T> {}
+}
+fn test(o: Option<u32>) {
+    (&o).as_ref();
+    o.as_ref();
+}
+"#,
+    );
+}
+
+#[test]
 fn infer_generic_chain() {
     check_inference(
         "infer_generic_chain",