Fix code generated matchers to handle recursive objects.

pkg/analysis_server/test/integration/integration_tests.dart

 // Copyright (c) 2014, 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 test.integration.analysis;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 438 matching lines @@
     } else {
       return iterableMatcher.describeMismatch(item, mismatchDescription,
           matchState, verbose);
     }
   }
 }
 
 Matcher isListOf(Matcher elementMatcher) => new _ListOf(elementMatcher);
 
 /**
+ * Type of closures used by LazyMatcher.
+ */
+typedef Matcher MatcherCreator();
+
+/**
+ * Wrapper class for Matcher which doesn't create the underlying Matcher object
+ * until it is needed.  This is necessary in order to create matchers that can
+ * refer to themselves (so that recursive data structures can be represented).
+ */
+class LazyMatcher implements Matcher {
+  /**
+   * Callback that will be used to create the matcher the first time it is
+   * needed.
+   */
+  final MatcherCreator _creator;
+
+  /**
+   * The matcher returned by [_creator], if it has already been called.
+   * Otherwise null.
+   */
+  Matcher _wrappedMatcher;
+
+  LazyMatcher(this._creator);
+
+  @override
+  Description describe(Description description) {
+    _createMatcher();
+    return _wrappedMatcher.describe(description);
+  }
+
+  @override
+  Description describeMismatch(item, Description mismatchDescription, Map matchState, bool verbose) {
+    _createMatcher();
+    return _wrappedMatcher.describeMismatch(item, mismatchDescription, matchState, verbose);
+  }
+
+  @override
+  bool matches(item, Map matchState) {
+    _createMatcher();
+    return _wrappedMatcher.matches(item, matchState);
+  }
+
+  /**
+   * Create the wrapped matcher object, if it hasn't been created already.
+   */
+  void _createMatcher() {
+    if (_wrappedMatcher == null) {
+      _wrappedMatcher = _creator();
+    }
+  }
+}
+
+/**
  * Matcher that matches a union of different types, each of which is described
  * by a matcher.
  */
 class _OneOf extends Matcher {
   /**
    * Matchers for the individual choices.
    */
   final List<Matcher> choiceMatchers;
 
   _OneOf(this.choiceMatchers);
@@ skipping 307 matching lines @@
    */
   void _recordStdio(String line) {
     double elapsedTime = _time.elapsedTicks / _time.frequency;
     line = "$elapsedTime: $line";
     if (_debuggingStdio) {
       print(line);
     }
     _recordedStdio.add(line);
   }
 }