My text is : Function(argument, function(argument)). When I use g4 DEBUGGER to generate the tree. It will works when there is blank between the last two parentheses: Function(argument, function(argument) ). But the debugger will say unexpected ‘))’ when there is not a blank. So, how should I revise my grammar to make it?
It confuses me a lot.
>Solution :
(It will be much easier to confirm the answer to your question if you post the grammar, or at least a stripped down version that demonstrates the issue. Note: Often, stripping down to a minimal example to demonstrate the issue will result in you finding your own answer.)
That said, based upon your error message, I would guess that you have a Lexer rule that matches )). If you do, then ANTLR will match that rule and create that token rather than creating two ) tokens.
Most of the time this mistake originates from not understanding that the Lexer is completely independent of the parser. The Lexer recognizes streams of characters and produces a stream of tokens, and then the parser matched rules against that stream of tokens. In this case, I would guess that the parser rule is looking to match a ) token, but finds the )) token instead. Those are two different tokens, so the parser rule will fail.