> On 19 Jun 2020, at 07:16, Akim Demaille <a...@lrde.epita.fr> wrote:
>
>> Le 18 juin 2020 à 20:46, Hans Åberg <haber...@telia.com> a écrit :
>>
>> Otherwise, in your link above you suggest not using the semantic value in
>> error messages, but when using locations, it contains the token
>> delimitations. So there seems to be no advantage letting the lexer
>> generating the error.
>
> It is still useful for the scanner to emit the error message, because the
> parser has no idea what is wrong. Granted, it knows _where_ it's wrong, but
> not _why_:
> - invalid character?
> - not-closed string?
> - invalid escape sequence?
> - out-of-range literal number?
> - etc.
>
> The scanner faces the error, *it* should say what's wrong.
Actually, I throw exceptions from the lexer, too. Like:
throw mli::my_parser::syntax_error(yylloc, "Directive syntax error.”);
In addition, I have warnings, which Bison does not support. A snippet that use
both errors and warnings:
if (unused_variable != true)
mli::my_parser::error(@x, "warning: " + ds);
else
throw syntax_error(@x, ds);
The error function checks if the string starts with “warning” and then does not
write the “error: “ part.
