[C++ Patch] PR 71238 ("Undeclared function message imprecisely points to error column")

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Hi,

this diagnostic bug report is about an incorrect column (normally the 
final closed parenthesis) for error messages emitted by 
unqualified_fn_lookup_error. The substance of the fix is obvious - pass 
an appropriate column information to the function - and it handles 
correctly all the instances I could find in the C++ testsuite, but there 
are a few implementation details that certainly could be different. Note 
that I also tried to be quite conservative, thus actively avoid 
UNKNOWN_LOCATION to ever get through. Eventually I'm proposing to change 
unqualified_fn_lookup_error to take a cp_expr instead of my initial idea 
of adding a location_t parameter: this way the call from 
cp_parser_postfix_expression - which accounts for about a third of the 
locations fixed in the testsuite - is automatically handled and only the 
call from perform_koenig_lookup needs a little adjustment, to wrap the 
location in a cp_expr together with the identifier. But admittedly I 
didn't follow in detail the discussion which led to the introduction of 
cp_expr, I'm not sure this kind of wrapping counts as an "appropriate" 
use. Tested x86_64-linux.

Thanks,
Paolo.

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