antlr4 在令牌中混合片段 [英] antlr4 mixed fragments in tokens

问题描述

我观察到一种奇怪的行为，尝试使用包含如下语句的语法来解析文本:

I observe a strange behavior, trying to parse a text using a grammar that contains a statements like the following:

fragment A : ('a'|'A') ;
fragment D : ('d'|'D') ;
fragment N : ('n'|'N') ;
KEY_AND : A N D;

我创建了一个简单的语法来产生我遇到的问题:

I created a simple grammar to produce the issue I experience:

grammar AndTest;  
mainRule: NAME SEP KEY_AND SEP NAME;
NAME: ('A'..'Z')+ ;
SEP: ';' ;
fragment A : ('a'|'A') ;
fragment D : ('d'|'D') ;
fragment N : ('n'|'N') ;
KEY_AND : A N D;
WS: [ \r\t\n]+ -> skip ;

在grun执行期间，我得到了以下信息(这里我们有'AND'并得到一个错误，但如果我们有'And'那么我们没有):

During grun execution I have got the following (here we have 'AND' and get an error, but if we have 'And' then we don't):

对于AND:echo ANDY ;和 ;安迪 |grun AndTest mainRule -tree

line 1:7 mismatched input 'AND' expecting KEY_AND
(mainRule ANDY ; AND ; ANDY)

for And: echo ANDY ;和 ;安迪 |grun AndTest mainRule -tree

(mainRule ANDY ; And ; ANDY)

我的问题:执行过程中发生的错误是预料之中的，我在语法中遗漏了一些东西，或者它是 antlr4 中的一种错误?

My question: The error occurred during execution is expected and I missed something in my grammar, or it is a kind of bug in antlr4?

环境:Windows7x32、Java SE 1.8.0_60-b27、antlr 4.5.1

Environment: Windows7x32, Java SE 1.8.0_60-b27, antlr 4.5.1

推荐答案

您的语法在匹配 NAME 规则之前将输入AND"匹配到 >KEY_AND 规则.

Your grammar is matching input "AND" to the NAME rule before is matches to the KEY_AND rule.

错误在意料之中.AND 满足NAME 的要求，并且NAME 列在之前 KEY_AND.规则的顺序在 antlr 中很重要.

The error is expected. AND meets the requirements for NAME and NAME is listed before KEY_AND. The order of rules is important in antlr.

将 KEY_AND 规则移到 NAME 上方应该可以修复此错误.

Moving the KEY_AND rule above NAME should fix this error.

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