Implement constant maps.

frog/leg/tree/nodes.dart

 // Copyright (c) 2011, 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.
 
 interface Visitor<R> {
   R visitBlock(Block node);
   R visitBreakStatement(BreakStatement node);
   R visitCatchBlock(CatchBlock node);
   R visitClassNode(ClassNode node);
   R visitConditional(Conditional node);
@@ skipping 734 matching lines @@
     if (other is !DartString) return false;
     DartString otherString = other;
     if (length != otherString.length) return false;
     Iterator it1 = iterator();
     Iterator it2 = otherString.iterator();
     while (it1.hasNext()) {
       if (it1.next() != it2.next()) return false;
     }
     return true;
   }
-  String toString() => "DartString#${length()}:${slowToString()}";
+  String toString() => "DartString#${length}:${slowToString()}";
   abstract SourceString get source();
 }
 
 class LiteralDartString extends DartString {
   final String string;
   const LiteralDartString(this.string);
   int get length() => string.length;
   Iterator<int> iterator() => new StringCodeIterator(string);
   String slowToString() => string;
   SourceString get source() => new StringWrapper(string);
@@ skipping 941 matching lines @@
   static bool isConstructorRedirect(Send node) {
     return (node.receiver === null &&
             node.selector.asIdentifier() !== null &&
             node.selector.asIdentifier().isThis()) ||
            (node.receiver !== null &&
             node.receiver.asIdentifier() !== null &&
             node.receiver.asIdentifier().isThis() &&
             node.selector.asIdentifier() !== null);
   }
 }