stdlib: add indicator tests for more custom AnyHashable representations that will be needed in future

Author: gribozavr

validation-test/stdlib/AnyHashableDiagnostics.swift

@@ -0,0 +1,13 @@
+// RUN: %target-parse-verify-swift
+
+// If this test fails, the following types started to conditionally conform to
+// `Hashable`.  When that happens, please add a custom `AnyHashable`
+// representation to corresponding Objective-C types.
+
+func isHashable<T : Hashable>(_: T.Type) {}
+
+isHashable(Int.self) // no-error // Test that `isHashable(_:)` works.
+
+isHashable(Array<Int>.self) // expected-error {{'Array<Int>' does not conform to expected type 'Hashable'}}
+isHashable(Dictionary<Int, Int>.self) // expected-error {{'Dictionary<Int, Int>' does not conform to expected type 'Hashable'}}
+