[TypeChecker] NFC: Add a test-case to test condition requirements interaction with transitive conformance checks

Author: xedin

test/Constraints/protocols.swift

@@ -454,3 +454,23 @@ func test_inference_through_implicit_conversion() {
   let _: UnsafePointer<C> = test([C()]) // Ok - argument is implicitly converted to a pointer
   let _: AnyHashable = test(C()) // Ok - argument is implicitly converted to `AnyHashable` because it's Hashable
 }
+
+// Make sure that conformances transitively checked through implicit conversions work with conditional requirements
+protocol TestCond {}
+
+extension Optional : TestCond where Wrapped == Int? {}
+
+func simple<T : TestCond>(_ x: T) -> T { x }
+
+func overloaded<T: TestCond>(_ x: T) -> T { x }
+func overloaded<T: TestCond>(_ x: String) -> T { fatalError() }
+
+func overloaded_result() -> Int { 42 }
+func overloaded_result() -> String { "" }
+
+func test_arg_conformance_with_conditional_reqs(i: Int) {
+  let _: Int?? = simple(i)
+  let _: Int?? = overloaded(i)
+  let _: Int?? = simple(overloaded_result())
+  let _: Int?? = overloaded(overloaded_result())
+}