add checks needed for covariant generics, and List<E>

lib/runtime/dart_runtime.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.
 
 var dart, _js_helper;
 (function (dart) {
   'use strict';
 
   let defineProperty = Object.defineProperty;
   let getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor;
@@ skipping 613 matching lines @@
     return to;
   }
 
   /**
    * Copy properties from source to destination object.
    * This operation is commonly called `mixin` in JS.
    */
   function copyProperties(to, from) {
     return copyPropertiesHelper(to, from, getOwnNamesAndSymbols(from));
   }
+  dart.copyProperties = copyProperties;
 
   /**
    * Copy symbols from the prototype of the source to destination.
    * These are the only properties safe to copy onto an existing public
    * JavaScript class.
    */
   function registerExtension(to, from) {
     return copyPropertiesHelper(to.prototype, from.prototype,
         getOwnPropertySymbols(from.prototype));
   }
+  dart.registerExtension = registerExtension;
 
-  dart.copyProperties = copyProperties;
-  dart.registerExtension = registerExtension;
+  function setBaseClass(derived, base) {
+    // Link the extension to the type it's extending as a base class.
+    derived.prototype.__proto__ = base.prototype;
+  }
+  dart.setBaseClass = setBaseClass;
 
   /**
    * This is called whenever a derived class needs to introduce a new field,
    * shadowing a field or getter/setter pair on its parent.
    *
    * This is important because otherwise, trying to read or write the field
    * would end up calling the getter or setter, and one of those might not even
    * exist, resulting in a runtime error. Even if they did exist, that's the
    * wrong behavior if a new field was declared.
    */
@@ skipping 203 matching lines @@
     // initializing them, but easier to not depend on that.
     for (let name of getOwnNamesAndSymbols(obj)) {
       // TODO(jmesserly): we can make this faster if needed.
       objectKey.push(name);
       objectKey.push(obj[name]);
     }
     return multiKeyPutIfAbsent(constants, objectKey, () => obj);
   }
   dart.const = constant;
 
-  /** Sets the runtime type of `obj` to be `type` */
+  /** Sets the type of `obj` to be `type` */
   function setType(obj, type) {
+    obj.__proto__ = type.prototype;
+  }
+  dart.setType = setType;
+
+  /** Sets the internal runtime type of `obj` to be `type` */
+  function setRuntimeType(obj, type) {
     obj[_runtimeType] = type;
   }
-  dart.setType = setType;
+  dart.setRuntimeType = setRuntimeType;
 
   // The following are helpers for Object methods when the receiver
   // may be null or primitive.  These should only be generated by
   // the compiler.
   function hashCode(obj) {
     if (obj == null) {
       return 0;
     }
     // TODO(vsm): What should we do for primitives and non-Dart objects?
     switch (typeof obj) {
@@ skipping 46 matching lines @@
   dart.bottom = { toString() { return 'bottom'; } };
 
   dart.global = window || global;
   dart.JsSymbol = Symbol;
 
   // TODO(jmesserly): hack to bootstrap the SDK
   _js_helper = _js_helper || {};
   _js_helper.checkNum = notNull;
 
 })(dart || (dart = {}));