Allowing `e` of any type in `void f(...) => e`

tests/language/void_block_return_test.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Testing that a void block function is not allowed to `return e`
+// where `e` is non-void.
+
+void foo() {
+  return 42; //# 00: static type warning
+}
+
+main() {
+  foo();
+}