fixes #40, extension methods for primitive types

tool/input_sdk/private/js_number.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 _interceptors;
 
 /**
  * The super interceptor class for [JSInt] and [JSDouble]. The compiler
  * recognizes this class as an interceptor, and changes references to
  * [:this:] to actually use the receiver of the method, which is
@@ skipping 323 matching lines @@
   Type get runtimeType => num;
 }
 
 /**
  * The interceptor class for [int]s.
  *
  * This class implements double since in JavaScript all numbers are doubles, so
  * while we want to treat `2.0` as an integer for some operations, its
  * interceptor should answer `true` to `is double`.
  */
+// TODO(jmesserly): for dev_compiler all numbers will get `int` members at
+// runtime for dynamic dispatch. We can fix by checking it at dispatch time.
+@JsPeerInterface(name: 'Number')
 class JSInt extends JSNumber implements int, double {
   const JSInt();
 
   bool get isEven => (this & 1) == 0;
 
   bool get isOdd => (this & 1) == 1;
 
   int toUnsigned(int width) {
     return this & ((1 << width) - 1);
   }
@@ skipping 59 matching lines @@
 }
 
 class JSDouble extends JSNumber implements double {
   const JSDouble();
   Type get runtimeType => double;
 }
 
 class JSPositiveInt extends JSInt {}
 class JSUInt32 extends JSPositiveInt {}
 class JSUInt31 extends JSUInt32 {}