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

dart/frog/leg/resolver.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.
 
 interface TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
 }
 
 class TreeElementMapping implements TreeElements {
@@ skipping 161 matching lines @@
     // [intrface] is an interface, let's say "MyInterface".
     // [defaultClass] is a class, let's say "MyClass".
 
     // First look up the constructor named "MyInterface.name".
     constructor.defaultImplementation =
       defaultClass.lookupConstructor(constructor.name);
 
     // If that fails, try looking up "MyClass.name".
     if (constructor.defaultImplementation === null) {
       SourceString name =
-          new SourceString(constructor.name.toString().replaceFirst(
-              intrface.name.toString(),
-              defaultClass.name.toString()));
+          new SourceString(constructor.name.slowToString().replaceFirst(
+              intrface.name.slowToString(),
+              defaultClass.name.slowToString()));
       constructor.defaultImplementation = defaultClass.lookupConstructor(name);
 
       if (constructor.defaultImplementation === null
           && name == defaultClass.name
           && constructor.computeParameters(compiler).parameterCount === 0) {
         constructor.defaultImplementation =
             defaultClass.getSynthesizedConstructor();
       }
 
       if (constructor.defaultImplementation === null) {
@@ skipping 171 matching lines @@
     } else {
       visitor.error(call, MessageKind.CONSTRUCTOR_CALL_EXPECTED);
       validTarget = false;
     }
 
     if (validTarget) {
       ResolverTask resolver = visitor.compiler.resolver;
       result = resolver.lookupConstructor(lookupTarget, call);
       if (result === null) {
         SourceString constructorName = resolver.getConstructorName(call);
-        SourceString className = lookupTarget.name;
+        String className = lookupTarget.name.slowToString();
         String name = (constructorName === const SourceString(''))
-                          ? className.stringValue
-                          : "$className.$constructorName";
+                          ? className
+                          : "$className.${constructorName.slowToString()}";
         error(call, MessageKind.CANNOT_RESOLVE_CONSTRUCTOR, [name]);
       } else {
         final Compiler compiler = visitor.compiler;
         // TODO(karlklose): support optional arguments.
         if (result.parameterCount(compiler) != call.argumentCount()) {
           error(call, MessageKind.NO_MATCHING_CONSTRUCTOR);
         }
       }
       visitor.useElement(call, result);
     }
@@ skipping 626 matching lines @@
 
   visitBreakStatement(BreakStatement node) {
     StatementElement target;
     if (node.target === null) {
       target = statementScope.currentBreakTarget();
       if (target === null) {
         error(node, MessageKind.NO_BREAK_TARGET);
         return;
       }
     } else {
-      String labelName = node.target.source.stringValue;
+      String labelName = node.target.source.slowToString();
       target = statementScope.lookupLabel(labelName);
       if (target === null) {
         error(node.target, MessageKind.UNBOUND_LABEL, [labelName]);
         return;
       }
     }
     target.isBreakTarget = true;
     mapping[node] = target;
   }
 
   visitContinueStatement(ContinueStatement node) {
     StatementElement target;
     if (node.target === null) {
       target = statementScope.currentContinueTarget();
       if (target === null) {
         error(node, MessageKind.NO_CONTINUE_TARGET);
         return;
       }
     } else {
-      String labelName = node.target.source.stringValue;
+      String labelName = node.target.source.slowToString();
       target = statementScope.lookupLabel(labelName);
       if (target === null) {
         error(node.target, MessageKind.UNBOUND_LABEL, [labelName]);
         return;
       }
       if (!target.origin.isValidContinueTarget()) {
         error(node.target, MessageKind.INVALID_CONTINUE, [labelName]);
       }
     }
     target.isContinueTarget = true;
@@ skipping 12 matching lines @@
         && (declaration is !VariableDefinitions ||
         !declaration.asVariableDefinitions().definitions.nodes.tail.isEmpty()))
     {
       // The variable declaration is either not an identifier, not a
       // declaration, or it's declaring more than one variable.
       error(node.declaredIdentifier, MessageKind.INVALID_FOR_IN, []);
     }
   }
 
   visitLabelledStatement(LabelledStatement node) {
-    String labelName = node.label.source.stringValue;
+    String labelName = node.label.source.slowToString();
     StatementElement existingElement = statementScope.lookupLabel(labelName);
     if (existingElement !== null) {
       LabelledStatement declaration = existingElement.origin;
       warning(node.label, MessageKind.DUPLICATE_LABEL, [labelName]);
       warning(declaration.label, MessageKind.EXISTING_LABEL, [labelName]);
     }
     StatementElement element =
         new StatementElement.label(labelName, node, enclosingElement);
     statementScope.enterLabelScope(labelName, element);
     visit(node.statement);
@@ skipping 342 matching lines @@
 class TopScope extends Scope {
   LibraryElement get library() => element;
 
   TopScope(LibraryElement library) : super(null, library);
   Element lookup(SourceString name) => library.find(name);
 
   Element add(Element element) {
     throw "Cannot add an element in the top scope";
   }
 }