---

yaml
---
r: 348129
b: refs/heads/master
c: 740e327
h: refs/heads/master
i:
  348127: bf2c39d

Author: swift-ci

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 98e9f1b5efa9336b6eb1e7ddb5e5764033a058c9
+refs/heads/master: 740e327cfe2d94ecf00c9da066421e1d9318e38d
 refs/heads/master-next: 203b3026584ecad859eb328b2e12490099409cd5
 refs/tags/osx-passed: b6b74147ef8a386f532cf9357a1bde006e552c54
 refs/tags/swift-2.2-SNAPSHOT-2015-12-01-a: 6bb18e013c2284f2b45f5f84f2df2887dc0f7dea

trunk/test/Constraints/protocols.swift

@@ -401,3 +401,20 @@ func rdar_50099849() {
   let _ = C<A, B>() // expected-error {{generic parameter 'C' could not be inferred}}
   // expected-note@-1 {{explicitly specify the generic arguments to fix this issue}} {{17-17=<<#C: Trivial#>>}}
 }
+
+// rdar://problem/50512161 - improve diagnostic when generic parameter cannot be deduced
+func rdar_50512161() {
+  struct Item {}
+
+  struct TrivialItem : Trivial {
+    typealias T = Item?
+  }
+
+  func foo<I>(_: I.Type = I.self, item: I.T) where I : Trivial { // expected-note {{in call to function 'foo(_:item:)'}}
+    fatalError()
+  }
+
+  func bar(_ item: Item) {
+    foo(item: item) // expected-error {{generic parameter 'I' could not be inferred}}
+  }
+}