令牌中的antlr4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，试图使用包含如下语句的语法分析文本:

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 ;

在执行grun期间，我得到了以下信息(这里我们有"AND"并得到一个错误，但是如果我们有"And"则没有):

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 ; AND ; ANDY | grun AndTest mainRule -tree

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

对于和:echo ANDY ; And ; ANDY | grun AndTest mainRule -tree

(mainRule ANDY ; And ; ANDY)

我的问题:预期在执行期间发生错误，我错过了语法中的某些内容，或者是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

您的语法先将输入"AND"与NAME规则匹配，然后再将其与KEY_AND规则匹配.

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

该错误是预期的. AND符合NAME的要求，并且NAME在之前 KEY_AND列出.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规则移至NAME上方可解决此错误.

Moving the KEY_AND rule above NAME should fix this error.

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