Fix issue in DeepMatcher where == throws.

pkg/unittest/lib/src/core_matchers.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.
 
 part of matcher;
 
 /**
  * Returns a matcher that matches empty strings, maps or iterables
  * (including collections).
  */
@@ skipping 112 matching lines @@
         return null;
       }
     }
     return null;
   }
 
   List _recursiveMatch(expected, actual, String location, int depth) {
     String reason = null;
     // If _limit is 1 we can only recurse one level into object.
     bool canRecurse = depth == 0 || _limit > 1;
-    if (expected == actual) {
+    bool equal;
+    try {
+      equal = (expected == actual);
+    } catch (e,s) {
+      // TODO(gram): Add a test for this case.
+      reason = '== threw "$e"';
+      return [reason, location];
+    }
+    if (equal) {
       // Do nothing.
     } else if (depth > _limit) {
       reason = 'recursion depth limit exceeded';
     } else {
       if (expected is Iterable && canRecurse) {
         List result = _compareIterables(expected, actual,
             _recursiveMatch, depth + 1, location);
         if (result != null) {
           reason = result[0];
           location = result[1];
@@ skipping 740 matching lines @@
     var innerDescription = new StringDescription();
     _matcher.describeMismatch(matchState['feature'], innerDescription,
         matchState['state'], verbose);
     if (innerDescription.length > 0) {
       mismatchDescription.add(' which ').add(innerDescription.toString());
     }
     return mismatchDescription;
   }
 }