Re: [PATCH] todo: short term

[Joel E. Denny]

On Thu, 17 Sep 2009, Akim Demaille wrote:

> +** Use syntax_error from the scanner?
> +This would provide a means to raise syntax error from function called
> +from the scanner.  Actually, there is no good solution to report a
> +lexical error in general.  Usually they are kept at the scanner level
> +only, ignoring the guilty token.  But that might not be the best bet,
> +since we don't benefit from the syntactic error recovery.
> +
> +We still have the possibility to return an invalid token number, which
> +does the trick.  But then the error message from the parser is poor
> +(something like "unexpected $undefined").

To fix that, use %token.

> Since the scanner probably
> +already reported the error, we should directly enter error-recovery,
> +without reporting the error message (i.e., YYERROR's semantics).

Maybe Bison can define a special token that the scanner can return to 
induce a YYERROR?  That seems simpler than a function call.