dart2js cps: Handle checks against mutable and extendable lists.

pkg/compiler/lib/src/js_backend/codegen/codegen.dart

 // Copyright (c) 2014, 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.
 
 library code_generator;
 
 import 'glue.dart';
 
 import '../../tree_ir/tree_ir_nodes.dart' as tree_ir;
 import '../../tree_ir/tree_ir_nodes.dart' show BuiltinOperator;
@@ skipping 319 matching lines @@
 
   @override
   js.Expression visitTypeOperator(tree_ir.TypeOperator node) {
     js.Expression value = visitExpression(node.value);
     List<js.Expression> typeArguments = visitExpressionList(node.typeArguments);
     DartType type = node.type;
     if (type is InterfaceType) {
       glue.registerIsCheck(type, registry);
       ClassElement clazz = type.element;
 
+      // Handle some special checks against classes that exist only in
+      // the compile-time class hierarchy, not at runtime.
+      if (clazz == glue.jsExtendableArrayClass) {
+        return js.js(r'!#.fixed$length', <js.Expression>[value]);
+      } else if (clazz == glue.jsMutableArrayClass) {
+        return js.js(r'!#.immutable$list', <js.Expression>[value]);
+      }
+
       // We use one of the two helpers:
       //
       //     checkSubtype(value, $isT, typeArgs, $asT)
       //     subtypeCast(value, $isT, typeArgs, $asT)
       //
       // Any of the last two arguments may be null if there are no type
       // arguments, and/or if no substitution is required.
       Element function = node.isTypeTest
           ? glue.getCheckSubtype()
           : glue.getSubtypeCast();
@@ skipping 400 matching lines @@
         return js.js("typeof # === 'number' && Math.floor(#) === #", args);
     }
   }
 
   visitFunctionExpression(tree_ir.FunctionExpression node) {
     // FunctionExpressions are currently unused.
     // We might need them if we want to emit raw JS nested functions.
     throw 'FunctionExpressions should not be used';
   }
 }