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:   }
  
    visitSwitchCase(SwitchCase node) {
      for (var expression in node.expressions) {
        writeIndentation();
        writeWord('case');
  
negative.code:   }
  
    visitLabeledStatement(LabeledStatement node) {
      writeIndentation();
      writeWord(syntheticNames.nameLabeledStatement(node));
      endLine(':');
      writeNode(node.body);
    }
  
    visitBreakStatement(BreakStatement node) {
      writeIndentation();
      writeWord('break');
      writeWord(syntheticNames.nameLabeledStatement(node.target));
      endLine(';');
    }
  
  