Use interceptors to handle runtime types.

dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.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 js_backend;
 
 /**
  * A function element that represents a closure call. The signature is copied
  * from the given element.
  */
@@ skipping 3141 matching lines @@
     }
     if (hasBool) {
       block.statements.add(buildInterceptorCheck(backend.jsBoolClass));
     }
     // TODO(ahe): It might be faster to check for Array before
     // function and bool.
     if (hasArray) {
       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);
       block.statements.add(
           js.if_(js('receiver instanceof #',
                     js(namer.isolateAccess(compiler.objectClass))),
                  js.return_(js('receiver'))));
       block.statements.add(
           js.return_(
               js(namer.isolateAccess(backend.getNativeInterceptorMethod))(
@@ skipping 1024 matching lines @@
 
 const String HOOKS_API_USAGE = """
 // The code supports the following hooks:
 // dartPrint(message)   - if this function is defined it is called
 //                        instead of the Dart [print] method.
 // dartMainRunner(main) - if this function is defined, the Dart [main]
 //                        method will not be invoked directly.
 //                        Instead, a closure that will invoke [main] is
 //                        passed to [dartMainRunner].
 """;