Merge pull request #9503 from DougGregor/rdar30154791-testcase

Add fixed crasher for rdar://problem/30154791.

Author: DougGregor

validation-test/compiler_crashers_2_fixed/0095-rdar30154791.swift

@@ -0,0 +1,35 @@
+// RUN: not %target-swift-frontend %s -typecheck
+
+struct X<T> {}
+struct Y<T> {}
+
+protocol P {
+  associatedtype T = X<U>
+  associatedtype U
+
+  func foo() -> T
+}
+
+protocol Q: P {
+  func bar() -> T
+  func bas() -> U
+}
+
+extension P {
+  func foo() -> X<U> { fatalError() }
+}
+
+extension Q {
+  func foo() -> Y<U> { fatalError() }
+  func bar() -> Y<U> { fatalError() }
+}
+
+struct S {}
+
+extension S {
+  func bas() -> Int {}
+}
+extension S: Q {}
+
+let x: Y = S().foo()
+