Compute correct constructor type for synthesized mixin constructors.

tests/language/checked_mode_helper.dart

+// Copyright (c) 2013, 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.
+
+library checked_mode_helper;
+
+import 'package:expect/expect.dart';
+
+/// Returns `true` if the program is running in checked mode.
+bool inCheckedMode() {
+  try {
+    var i = 42;
+    String s = i;
+  } on TypeError catch (e) {
+    return true;
+  }
+  return false;
+}
+
+/// Checks that a dynamic type error is thrown if and only if [f] is executed in
+/// checked mode and [expectTypeError] is `true`.
+void testDynamicTypeError(bool expectTypeError, f(), [String message]) {
+  if (expectTypeError) {
+    checkDynamicTypeError(f, message);
+  } else {
+    checkNoDynamicTypeError(f, message);
+  }
+}
+
+/// Checks that a dynamic type error is thrown if and only if [f] is executed in
+/// checked mode.
+void checkDynamicTypeError(f(), [String message]) {
+  message = message != null ? ': $message' : '';
+  try {
+    f();
+    Expect.isFalse(inCheckedMode(),
+      'Missing type error in checked mode$message.');
+  } on TypeError catch (e) {
+    Expect.isTrue(inCheckedMode(),
+      'Unexpected type error in production mode.');
+  }
+}
+
+/// Checks that no dynamic type error is thrown when [f] is executed regardless
+/// of execution mode.
+void checkNoDynamicTypeError(f(), [String message]) {
+  message = message != null ? ': $message' : '';
+  try {
+    f();
+  } on TypeError catch (e) {
+    String mode = inCheckedMode() ? 'checked mode' : 'production mode';
+    Expect.fail('Unexpected type error in $mode$message.');
+  }
+}