Use interceptors to handle runtime types.

dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

Index: dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart b/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
index 3118874217d4d8cebfdf1478105c9cb3c626cab5..a951b0a565a515463eb1352b4f0fd29017ca8f89 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -3159,11 +3159,23 @@ class CodeEmitterTask extends CompilerTask {
       block.statements.add(buildInterceptorCheck(backend.jsArrayClass));
     }
 
+    // TODO(ahe): Work with sra@ to integrate this with native interceptors,
+    // and potentially initialize the dispatch object during finishClasses.

[ngeoffray, 2013/09/06 06:54:06]

Please add a comment on what this is for, and what does builtin$cls means.

[ahe, 2013/09/09 11:26:29]

Done.

+    block.statements.add(
+        js.if_(r'typeof receiver == "function" && "builtin$cls" in receiver',
+               buildReturnInterceptor(backend.jsRuntimeType)));
+
+    // TODO(ahe): This should be a constant and we should be able to remove
+    // this test (so I'm keeping the redundant "object" test).

[ngeoffray, 2013/09/06 06:54:06]

Ditto for having "func"

[ahe, 2013/09/09 11:26:29]

Done.

+    block.statements.add(
+        js.if_(r'typeof receiver == "object"'
+               ' && receiver.constructor === Object'

[ngeoffray, 2013/09/06 06:54:06]

Add a comment on why this constructor check?

[ahe, 2013/09/09 11:26:29]

Done.

+               ' && "func" in receiver',
+               buildReturnInterceptor(backend.jsFunctionType)));
+
     if (hasNative) {
       block.statements.add(
-          js.if_(
-              js('(typeof receiver) != "object"'),
-              js.return_(js('receiver'))));
+          js.if_('typeof receiver != "object"', js.return_('receiver')));
 
       // if (receiver instanceof $.Object) return receiver;
       // return $.getNativeInterceptor(receiver);