anchor.diff:  
     accept(Visitor visitor) => visitor.visitThrow(this);
   
  +  accept1(Visitor1 visitor, arg) => visitor.visitThrow(this, arg);
  +
     visitChildren(Visitor visitor) {
       expression.accept(visitor);
  +  }
  +
  +  visitChildren1(Visitor1 visitor, arg) {
  +    expression.accept1(visitor, arg);
     }
   
     Token getBeginToken() => throwToken;
  
positive.code: 
    accept(Visitor visitor) => visitor.visitExport(this);
  
    visitChildren(Visitor visitor) {
      uri.accept(visitor);
      if (combinators != null) combinators.accept(visitor);
    }
  
    Token getBeginToken() => exportKeyword;
  
negative.code: 
    accept(Visitor visitor) => visitor.visitNamedMixinApplication(this);
  
    accept1(Visitor1 visitor, arg) {
      return visitor.visitNamedMixinApplication(this, arg);
    }
  
    visitChildren(Visitor visitor) {
      name.accept(visitor);
      if (typeParameters != null) typeParameters.accept(visitor);
  