Simplify runtime type support.

sdk/lib/_internal/compiler/implementation/js/nodes.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;
 
 abstract class NodeVisitor<T> {
   T visitProgram(Program node);
 
   T visitBlock(Block node);
@@ skipping 695 matching lines @@
   int get precedenceLevel => CALL;
 }
 
 class PropertyAccess extends Expression {
   final Expression receiver;
   final Expression selector;
 
   PropertyAccess(this.receiver, this.selector);
   PropertyAccess.field(this.receiver, String fieldName)
       : selector = new LiteralString("'$fieldName'");
+  PropertyAccess.indexed(this.receiver, int index)
+      : selector = new LiteralNumber('$index');
 
   accept(NodeVisitor visitor) => visitor.visitAccess(this);
 
   void visitChildren(NodeVisitor visitor) {
     receiver.accept(visitor);
     selector.accept(visitor);
   }
 
   int get precedenceLevel => CALL;
 }
@@ skipping 106 matching lines @@
   /** Contains the pattern and the flags.*/
   String pattern;
 
   RegExpLiteral(this.pattern);
 
   accept(NodeVisitor visitor) => visitor.visitRegExpLiteral(this);
   void visitChildren(NodeVisitor visitor) {}
 
   int get precedenceLevel => PRIMARY;
 }