如何在 ANTLR4 中终止词法分析器

问题描述

是否有一种简单的方法可以终止词法分析器?

Is there a simple way to terminate a lexer?

有些令牌我还不想处理.但我也希望 Lexer 在输入确实包含这些标记时发出警报.我的简单策略是在一个动作中抛出一个 RuntimeException:

There are some tokens that I do not want to handle yet. But I also want the Lexer to sound an alarm if the input does contain those tokens. My simple strategy is throwing a RuntimeException in an action:

CHARIZING:  '#@' {throw new RuntimeException("charizing op not supported yet");};

但是该操作会产生编译错误，因为生成的 Lexer 在该操作之后有一个 break 命令，并且 Java 编译器抱怨 break 是一个无法访问的语句.

But the action produces compilation error since the generated Lexer has a break command after the action and the Java compiler complains the break is an unreachable statement.

CPPDefineLexer.java:118: error: unreachable statement
                case 1: throw new RuntimeException("charizing op not supported y
et"); break;

是否有终止 Lexer 的简单策略?

Is there a simple strategy to terminate a Lexer?

推荐答案

你可以欺骗编译器:

CHARIZING
 : '#@'
   {
     if (true) { throw new RuntimeException("charizing op not supported yet"); }
   }
 ;

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