Return null from stringValue and call slowToString() instead of toString().

dart/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 564 matching lines @@
 
 class LiteralInt extends Literal<int> {
   LiteralInt(Token token, DecodeErrorHandler handler) : super(token, handler);
 
   LiteralInt asLiteralInt() => this;
 
   int get value() {
     try {
       Token token = this.token;
       if (token.kind === PLUS_TOKEN) token = token.next;
-      return Math.parseInt(token.value.toString());
+      return Math.parseInt(token.value.slowToString());
     } catch (BadNumberFormatException ex) {
       (this.handler)(token, ex);
     }
   }
 
   accept(Visitor visitor) => visitor.visitLiteralInt(this);
 }
 
 class LiteralDouble extends Literal<double> {
   LiteralDouble(Token token, DecodeErrorHandler handler)
     : super(token, handler);
 
   LiteralDouble asLiteralDouble() => this;
 
   double get value() {
     try {
       Token token = this.token;
       if (token.kind === PLUS_TOKEN) token = token.next;
-      return Math.parseDouble(token.value.toString());
+      return Math.parseDouble(token.value.slowToString());
     } catch (BadNumberFormatException ex) {
       (this.handler)(token, ex);
     }
   }
 
   accept(Visitor visitor) => visitor.visitLiteralDouble(this);
 }
 
 class LiteralBool extends Literal<bool> {
   LiteralBool(Token token, DecodeErrorHandler handler) : super(token, handler);
@@ skipping 126 matching lines @@
   final int length;
   SourceBasedDartString(this.source, this.length);
   abstract Iterator<int> iterator();
 }
 
 class RawSourceDartString extends SourceBasedDartString {
   RawSourceDartString(source, length) : super(source, length);
   Iterator<int> iterator() => source.iterator();
   String toString() {
     if (toStringCache !== null) return toStringCache;
-    toStringCache  = source.stringValue;
+    toStringCache  = source.slowToString();
     return toStringCache;
   }
 }
 
 class EscapedSourceDartString extends SourceBasedDartString {
   EscapedSourceDartString(source, length) : super(source, length);
   Iterator<int> iterator() {
     if (toStringCache !== null) return new StringCodeIterator(toStringCache);
     return new StringEscapeIterator(source);
   }
@@ skipping 163 matching lines @@
 }
 
 class Identifier extends Expression {
   final Token token;
 
   SourceString get source() => token.value;
 
   Identifier(Token this.token);
   Identifier.synthetic(String name) : token = new StringToken(null, name, null);
 
-  bool isThis() => source.stringValue == 'this';
+  bool isThis() => source.stringValue === 'this';
 
-  bool isSuper() => source.stringValue == 'super';
+  bool isSuper() => source.stringValue === 'super';
 
   Identifier asIdentifier() => this;
 
   accept(Visitor visitor) => visitor.visitIdentifier(this);
 
   visitChildren(Visitor visitor) {}
 
   Token getBeginToken() => token;
 
   Token getEndToken() => token;
@@ skipping 603 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);
   }
 }