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..284715d245a936361b175bcf1b5ccdccabbd03e4 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -3159,18 +3159,35 @@ class CodeEmitterTask extends CompilerTask {
       block.statements.add(buildInterceptorCheck(backend.jsArrayClass));
     }
 
+    // Recognize JavaScript functions that correspond to Dart constructors
+    // (generated by defineClass that adds the property 'builtin$cls').
+    // TODO(ahe): Either integrate this with native dispatchProperty, or use a
+    // mixin approach in defineClass.
+    block.statements.add(
+        js.if_(r'typeof receiver == "function" && "builtin$cls" in receiver',
+               buildReturnInterceptor(backend.jsRuntimeType)));
+
+    // Recognize JavaScript object literals that are used to encode function
+    // types. These objects are generated by
+    // [TypeRepresentationGenerator.visitFunctionType] and always have the

[ngeoffray, 2013/09/10 10:42:26]

missing something after 'and'.

+    // "func" property (namer.functionTypeTag()).
+    // TODO(ahe): This should be a real Dart object and we should be able to
+    // remove this test (so I'm keeping the redundant "object" test).
+    block.statements.add(
+        js.if_(r'typeof receiver == "object"'
+               // JavaScript object literals have Object as constructor.
+               ' && receiver.constructor === Object'
+               ' && "${namer.functionTypeTag()}" 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);
       block.statements.add(
           js.if_(js('receiver instanceof #',
                     js(namer.isolateAccess(compiler.objectClass))),
-                 js.return_(js('receiver'))));
+                 js.return_('receiver')));
       block.statements.add(
           js.return_(
               js(namer.isolateAccess(backend.getNativeInterceptorMethod))(