如何在ANTLR 4中创建一个可以捕获不同类型的词法错误的词法分析器 [英] How to create a lexical analyzer in ANTLR 4 that can catch different types of lexical errors

问题描述

我使用ANTLR 4创建我的词法分析器，但我不知道如何创建一个词法分析器捕获不同类型的词法错误。

I am using ANTLR 4 to create my lexer, but I don't how to create a lexical analyzer that catches different types of lexical errors.

例如：

1. 如果我有一个无法识别的符号，例如 ^

如果我有一个无效的标识符 2n 词汇分析器应报告此类错误identifier2n必须以字母

If I have an invalid identifier like 2n the lexical analyzer should report an error like this "identifier "2n" must begin with a letter"

推荐答案

为每个已知错误和catchall错误标记规则创建错误标记规则像这样：

Create an error token rule for each known error and an "catchall" error token rule at the end like this:

// valid tokens first!
Number : [0-9]+;
Identifier : [a-zA-Z] [a-zA-Z0-9]*;
//...

// "error" tokens
// don't use these tokens in your grammar; They will show up as extraneous tokens during parsing and can be handled if desired.
InvalidIdentifier : [0-9]([0-9a-zA-Z])+; 
ACommonInvalidToken : '^'; // if you want to be more specific for certain cases
// add more to address common mistakes

UnknownToken : . ; // the "catch-all" error token; be sure not to be too greedy...

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