Fix issue 24043: do not trust the pattern. Enable a 'hidden' test.

tests/language/string_interpolation_and_buffer.dart

-// Copyright (c) 2012, 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.
-
-// Test to ensure that StringBuffer and string interpolation behaves
-// the same and fail fast.
-
-class ToStringWrapper {
-  final value;
-
-  ToStringWrapper(this.value);
-
-  toString() => value;
-}
-
-wrap(value) => new ToStringWrapper(value);
-
-main() {
-  bool checkedMode = false;
-  assert(checkedMode = true);
-  interpolate(object) {
-    var result;
-    if (checkedMode && object != null) {
-      try {
-        result = '${wrap(object)}';
-      } on TypeError {
-        return 'Error';
-      }
-    } else {
-      try {
-        result = '${wrap(object)}';
-      } on ArgumentError {
-        return 'Error';
-      }
-    }
-    Expect.isTrue(result is String);
-    return 'Success';
-  }
-
-  buffer(object) {
-    var sb;
-    if (checkedMode && object != null) {
-      try {
-        sb = new StringBuffer()..write(wrap(object));
-      } on TypeError {
-        return 'Error';
-      }
-    } else {
-      try {
-        sb = new StringBuffer()..write(wrap(object));
-      } on ArgumentError {
-        return 'Error';
-      }
-      Expect.isTrue(sb.toString() is String);
-    }
-    return 'Success';
-  }
-
-  initBuffer(object) {
-    var sb;
-    if (checkedMode && object != null) {
-      try {
-        sb = new StringBuffer(wrap(object));
-      } on TypeError {
-        return 'Error';
-      }
-    } else {
-      try {
-        sb = new StringBuffer(wrap(object));
-      } on ArgumentError {
-        return 'Error';
-      }
-      Expect.isTrue(sb.toString() is String);
-    }
-    return 'Success';
-  }
-
-  Expect.equals('Error', interpolate(null));
-  Expect.equals('Success', interpolate(""));
-  Expect.equals('Success', interpolate("string"));
-  Expect.equals('Error', interpolate([]));
-  Expect.equals('Error', interpolate([1]));
-  Expect.equals('Error', interpolate(new Object()));
-
-  Expect.equals('Error', buffer(null));
-  Expect.equals('Success', buffer(""));
-  Expect.equals('Success', buffer("string"));
-  Expect.equals('Error', buffer([]));
-  Expect.equals('Error', buffer([1]));
-  Expect.equals('Error', buffer(new Object()));
-
-  Expect.equals('Error', initBuffer(null));
-  Expect.equals('Success', initBuffer(""));
-  Expect.equals('Success', initBuffer("string"));
-  Expect.equals('Error', initBuffer([]));
-  Expect.equals('Error', initBuffer([1]));
-  Expect.equals('Error', initBuffer(new Object()));
-}