anchor.diff:    final Namer<Class> classes = new Namer<Class>('#class');
     final Namer<Library> libraries = new Namer<Library>('#lib');
     final Namer<TypeParameter> typeParameters = new Namer<TypeParameter>('#T');
  +  final Namer<TreeNode> labels = new Namer<TreeNode>('#L');
     final Disambiguator<Library> prefixes = new Disambiguator<Library>();
   
     nameVariable(VariableDeclaration node) => variables.getName(node);
  
positive.code:   nameClass(Class node) => classes.getName(node);
    nameLibrary(Library node) => libraries.getName(node);
    nameTypeParameter(TypeParameter node) => typeParameters.getName(node);
  
    nameLibraryPrefix(Library node, {String proposedName}) {
      return prefixes.disambiguate(node, () {
  
negative.code: 
    visitContinueSwitchStatement(ContinueSwitchStatement node) {
      writeIndentation();
      writeWord('continue');
      writeWord(syntheticNames.nameSwitchCase(node.target));
      endLine(';');
    }
  
  