tests/language/regress/regress26133_test.dart

// Copyright (c) 2016, 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.

import 'dart:async';

var x = 'a';

Future<int> foo() async {
  return x;
  //     ^
  // [analyzer] COMPILE_TIME_ERROR.RETURN_OF_INVALID_TYPE
  // [cfe] A value of type 'String' can't be returned from an async function with return type 'Future<int>'.
}

main() {
  foo();
}