Skip type checks on native JavaScriptObjects

lib/runtime/_operations.js

 // Copyright (c) 2015, 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.
 
 /* This library defines runtime operations on objects used by the code
  * generator.
  */
 dart_library.library('dart_runtime/_operations', null, /* Imports */[
 ], /* Lazy Imports */[
   'dart/async',
@@ skipping 174 matching lines @@
         isSubtype(type, async.StreamSubscription) &&
             isSubtype(actual, async.StreamSubscription)) {
       console.warn('Ignoring cast fail from ' + types.typeName(actual) +
         ' to ' + types.typeName(type));
       return true;
     }
     return false;
   }
 
   function strongInstanceOf(obj, type) {
-    return types.isSubtype(rtti.realRuntimeType(obj), type);
+    let actual = rtti.realRuntimeType(obj);
+    return types.isSubtype(actual, type) || actual == types.jsobject;
   }
   exports.strongInstanceOf = strongInstanceOf;
 
   function instanceOfOrNull(obj, type) {
     if ((obj == null) || strongInstanceOf(obj, type)) return true;
     return false;
   }
 
   function instanceOf(obj, type) {
     if (strongInstanceOf(obj, type)) return true;
-    // TODO(vsm): This is perhaps too eager to throw a StrongModeError?
+    // TODO(#296): This is perhaps too eager to throw a StrongModeError?
     // It will throw on <int>[] is List<String>.
     // TODO(vsm): We can statically detect many cases where this
     // check is unnecessary.
     if (types.isGroundType(type)) return false;
     let actual = rtti.realRuntimeType(obj);
     dart_utils.throwStrongModeError('Strong mode is check failure: ' +
       types.typeName(actual) + ' does not soundly subtype ' +
       types.typeName(type));
   }
   exports.instanceOf = instanceOf;
 
   function cast(obj, type) {
+    // TODO(#296): This is perhaps too eager to throw a StrongModeError?
     // TODO(vsm): handle non-nullable types
     if (instanceOfOrNull(obj, type)) return obj;
     let actual = rtti.realRuntimeType(obj);
-    if (_ignoreTypeFailure(actual, type)) {
-      // TODO(vsm): track why this is happening in our async / await tests.
-      if (types.isGroundType(type)) {
-        console.error('Should not ignore cast failure from ' +
-          types.typeName(actual) + ' to ' + types.typeName(type));
-      }
-      return obj;
-    }
-    if (types.isGroundType(type)) {
-      errors.throwCastError(actual, type);
-    }
+    if (types.isGroundType(type)) errors.throwCastError(actual, type);
+
+    if (_ignoreTypeFailure(actual, type)) return obj;
+
     dart_utils.throwStrongModeError('Strong mode cast failure from ' +
       types.typeName(actual) + ' to ' + types.typeName(type));
   }
   exports.cast = cast;
 
   function arity(f) {
     // TODO(jmesserly): need to parse optional params.
     // In ES6, length is the number of required arguments.
     return { min: f.length, max: f.length };
   }
@@ skipping 191 matching lines @@
     next() {
       let i = this.dartIterator;
       let done = !i.moveNext();
       return { done: done, value: done ? void 0 : i.current };
     }
   }
   exports.JsIterator = JsIterator;
 
 
 });