Implement InstanceMirror.== in dart2js and InstanceMirror.hashCode in the VM and …

sdk/lib/_internal/lib/js_mirrors.dart

Index: sdk/lib/_internal/lib/js_mirrors.dart
diff --git a/sdk/lib/_internal/lib/js_mirrors.dart b/sdk/lib/_internal/lib/js_mirrors.dart
index 88decfe41e335b24be18c46d811b255c54ac3a03..e826fd2078bb0e17687005b00375501bef72c587 100644
--- a/sdk/lib/_internal/lib/js_mirrors.dart
+++ b/sdk/lib/_internal/lib/js_mirrors.dart
@@ -29,7 +29,8 @@ import 'dart:_js_helper' show
     runtimeTypeToString;
 import 'dart:_interceptors' show
     Interceptor,
-    JSExtendableArray;
+    JSExtendableArray,
+    getInterceptor;

[ahe, 2013/08/30 20:40:14]

I think you can remove this import if my suggestion below works.

[rmacnak, 2013/08/30 21:08:29]

Done.

 import 'dart:_js_names';
 
 /// No-op method that is called to inform the compiler that tree-shaking needs
@@ -677,6 +678,22 @@ class JsInstanceMirror extends JsObjectMirror implements InstanceMirror {
     return JSInvocationMirror.invokeFromMirror(invocation, reflectee);
   }
 
+  operator ==(other) {
+    return other is JsInstanceMirror &&
+           identical(reflectee, other.reflectee);
+  }
+
+  int get hashCode {
+    // If the reflectee is intercepted, use the base hashCode to preserve the
+    // illusion that, e.g. doubles, with the same value are identical.
+    // Otherwise, use the primitive identity hash to maintain correctness even
+    // if a user-defined hashCode returns different values for successive
+    // invocations.
+    return getInterceptor(reflectee) is Interceptor

[ahe, 2013/08/30 20:40:14]

I think other native types, such as DivElement, will return true here.

So I think it would be better to use this test:

return (JS('bool', 'typeof # == "object"', reflectee)) ?
Primitives.objectHashCode(reflectee) : reflectee.hashCode;

[rmacnak, 2013/08/30 21:08:29]

Done, but I have to also separate out null. typeof null == "object", but
Primitives.objectHashCode(null) does not work (TypeError: Cannot read property
'$identityHash' of null).

+        ? reflectee.hashCode
+        : Primitives.objectHashCode(reflectee);
+  }
+
   String toString() => 'InstanceMirror on ${Error.safeToString(reflectee)}';
 
   // TODO(ahe): Remove this method from the API.