ANTLR语法错误意外令牌:加 [英] ANTLR syntax error unexpected token: plus

问题描述

我的ANTLR树语法有一个小问题.我正在使用ANTLRWorks 1.4.在解析器语法中，我有如下规则:

Hi I have a small problem in my ANTLR tree grammar. I am using ANTLRWorks 1.4. In parser grammar I have the rule like this:

declaration
:       'variable' IDENTIFIER ( ',' IDENTIFIER)* ':' TYPE ';'
->    ^('variable' IDENTIFIER TYPE)+

所以我希望每个IDENTIFIER都有一棵树.

So I wanted one tree per each IDENTIFIER.

在树语法中，我只保留了重写规则:

And in the tree grammar I left only rewrite rules:

declaration
:     ^('variable' IDENTIFIER TYPE)+

但是当我检查语法时，出现语法错误意外的标记+.它是树语法中声明规则末尾的+号.那我做错了吗?

But when I check grammar I got syntax error unexpected token +. And it is this + sign at the end of the declaration rule in the tree grammar. So what I am doing wrong?

解析器语法可以正常工作，并且可以按预期构建AST树.我为C#生成了词法分析器和解析器，并对其进行了一些输入测试.

Parser grammar works fine and builds AST tree as expected. I generated lexer and parser for C# and test it for some input.

推荐答案

解析源代码时:

variable a, b, c : int;

您正在尝试构建如下所示的AST:

you're trying to construct an AST that looks like:

variable variable variable
    /        |        \
   a         b         c
  /          |          \
int         int         int

但是，由于'variable'和TYPE始终是相同的标记，因此我认为无需创建所有这些重复的节点.为什么不这样做:

But since 'variable' and TYPE are always the same token, I see no need to create all those duplicate nodes. Why not just do:

declaration
  :  'variable' IDENTIFIER ( ',' IDENTIFIER)* ':' TYPE ';' 
     -> ^('variable' TYPE IDENTIFIER+)
  ;

这将创建类似AST的

 variable
  / | | \
int a b  c

?

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