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ANTLR: parsing two-digit numbers when other numeric literals are possible

I am writing a grammar for a moderate sized language and I am trying to implement temporary form literals hh:mm:ss

.

However, whenever I try to parse, like 12:34:56

how timeLiteral

, I get inappropriate token exceptions on the numbers. Does anyone know what I might be doing wrong?

The following are the relevant rules:

timeLiteral
    :   timePair COLON timePair COLON timePair -> ^(TIMELIT timePair*)
    ;

timePair
    :   DecimalDigit DecimalDigit
    ;

NumericLiteral
    : DecimalLiteral
    ;

fragment DecimalLiteral
    : DecimalDigit+ ('.' DecimalDigit+)?
    ;

fragment DecimalDigit
    : ('0'..'9')
    ;
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The problem is that the lexer is consuming the DecimalDigit and returning a NumericLiteral.

The parser will never see DecimalDigits because it is a fragment rule.

I would recommend moving the timeLiteral to lexer (capital letters of its name). This way you will have something like



timeLiteral
    :   TimeLiteral -> ^(TIMELIT TimeLiteral*)
    ;

number
    :   DecimalLiteral
    ;

TimeLiteral
    :   DecimalDigit DecimalDigit COLON 
        DecimalDigit DecimalDigit COLON
        DecimalDigit DecimalDigit
    ;

DecimalLiteral
    :   DecimalDigit+ ('.' DecimalDigit+)?
    ;

fragment DecimalDigit
    :   ('0'..'9')
    ;

Keep in mind that the lexer and parser are completely independent. The lexer determines which tokens will be passed to the parser, then the parser will group them.

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