regex miscompilation on trivial cases

[JohanVonElectrum]

This is probably a duplicate of #500, but I'm not sure, so I'm opening this issue.

I'm experiencing some issues with this crate and have been creating a minimal POC/test to track it down.

use logos::Logos;

#[derive(Logos, Debug)]
enum TokenKind {
    #[regex("[0-9]+(_+[0-9]+)*")]
    DecInt,
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_lexer() {
        let source = "123_";
        let mut lexer = TokenKind::lexer(source).spanned();
        assert_eq!("", lexer.slice(), "Initial lexer slice should be empty");
        assert_eq!(source, lexer.remainder(), "Initial lexer remainder should match source");
        let (result, span) = lexer.next().unwrap();
        let slice = &source[span];
        assert_eq!("123", lexer.slice(), "Lexer slice should be '123'");
        assert_eq!("_", lexer.remainder(), "Lexer remainder should be '_'");
        match result {
            Ok(TokenKind::DecInt) => (),
            Err(_) => panic!("Unexpected error"),
        }
        assert_eq!(slice, "123");
    }
}

This should lex DecInt tokens with this regex ([0-9]+(_+[0-9]+)*):

For the input 123_, I expect a TokenKind::DecInt with slice 123 (without _), but I get Lexer slice should be '123' Left: 123 Right: 123_ and if I comment out both assert_eq before the match (

-        assert_eq!("123", lexer.slice(), "Lexer slice should be '123'");
+        // assert_eq!("123", lexer.slice(), "Lexer slice should be '123'");
-        assert_eq!("_", lexer.remainder(), "Lexer remainder should be '_'");
+        // assert_eq!("_", lexer.remainder(), "Lexer remainder should be '_'");

) I get an Unexpected error.

[robot-rover]

Fixed by #491!