如何在 ANTLR 4 中创建可以捕获不同类型词法错误的词法分析器

问题描述

我正在使用 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来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. 如果我有一个像 ^ 这样无法识别的符号，词法分析器应该会报告这样的错误无法识别的符号^""

1. If I have an unrecognized symbol like ^ the lexical analyzer should a report an error like this "Unrecognized symbol "^" "

如果我有一个像 2n 这样的无效标识符，词法分析器应该报告这样的错误标识符2n"必须以字母开头"

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

请你帮帮我.

推荐答案

为每个已知错误创建一个错误标记规则，并在末尾创建一个catchall"错误标记规则，如下所示:

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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