Fix JSON encoder accepting NaN and Infinity.

sdk/lib/convert/json.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.
 
 part of dart.convert;
 
 /**
  * Error thrown by JSON serialization if an object cannot be serialized.
  *
  * The [unsupportedObject] field holds that object that failed to be serialized.
@@ skipping 408 matching lines @@
   }
 
   /**
    * Serializes a [num], [String], [bool], [Null], [List] or [Map] value.
    *
    * Returns true if the value is one of these types, and false if not.
    * If a value is both a [List] and a [Map], it's serialized as a [List].
    */
   bool stringifyJsonValue(final object) {
     if (object is num) {
-      // TODO: use writeOn.
+      if (!object.isFinite) return false;
       sink.write(numberToString(object));
       return true;
     } else if (identical(object, true)) {
       sink.write('true');
       return true;
     } else if (identical(object, false)) {
       sink.write('false');
        return true;
     } else if (object == null) {
       sink.write('null');
       return true;
     } else if (object is String) {
       sink.write('"');
       escape(sink, object);
       sink.write('"');
       return true;
     } else if (object is List) {
       checkCycle(object);
       List a = object;
       sink.write('[');
       if (a.length > 0) {
         stringifyValue(a[0]);
-        // TODO: switch to Iterables.
         for (int i = 1; i < a.length; i++) {
           sink.write(',');
           stringifyValue(a[i]);
         }
       }
       sink.write(']');
       seen.remove(object);
       return true;
     } else if (object is Map) {
       checkCycle(object);
@@ skipping 12 matching lines @@
         first = false;
       });
       sink.write('}');
       seen.remove(object);
       return true;
     } else {
       return false;
     }
   }
 }