[embedded] Add metatypes.swift test showing a diagnostic when using metatypes

Author: kubamracek

test/embedded/metatypes.swift

@@ -0,0 +1,14 @@
+// RUN: %target-swift-emit-ir -verify %s -enable-experimental-feature Embedded -wmo
+
+// REQUIRES: optimized_stdlib
+// REQUIRES: VENDOR=apple
+// REQUIRES: OS=macosx
+
+public func sink<T>(t: T) {}
+
+public func test() -> Int {
+  let metatype = Int.self
+  sink(t: metatype) // expected-error {{cannot use metatype 'Int' in embedded Swift}}
+  // expected-note@-1 {{called from here}}
+  return 42
+}