On 14 May 2014 18:47, Jason Merrill <ja...@redhat.com> wrote:
> When I was working on DR 1571, I noticed that our diagnostics weren't very
> helpful for reference bindings (BZ 20332/21631) so I set out to treat
> lvalue/rvalue mismatches and cv-qual loss as a bad conversion rather than no
> conversion. As I worked on that I kept noticing other things that I could
> tweak to improve diagnostics:
>
> We now explain what's wrong with near matches in overload resolution. As a
> result, I've changed to saying "candidate:" before every candidate to help
> users recognize when we're printing a new candidate rather than explanation
> of what was wrong with the previous one.
>
> We now get information about near-matches even with -pedantic.
>
> If we see ambiguous valid candidates, the diagnostic won't mention
> near-matches. If we see a template candidate and ambiguous near-valid
> candidates, we will print all the candidates.
>
> Tested x86_64-pc-linux-gnu, applying to trunk.
This looks great. One minor nit: In this hunk, what is input_location
pointing at and why is that better than loc?
@@ -3195,18 +3217,37 @@ equal_functions (tree fn1, tree fn2)
static void
print_conversion_rejection (location_t loc, struct conversion_info *info)
{
+ tree from = info->from;
+ if (!TYPE_P (from))
+ from = lvalue_type (from);
if (info->n_arg == -1)
- /* Conversion of implicit `this' argument failed. */
- inform (loc, " no known conversion for implicit "
- "%<this%> parameter from %qT to %qT",
- info->from_type, info->to_type);
+ {
+ /* Conversion of implicit `this' argument failed. */
+ if (!TYPE_P (info->from))
+ /* A bad conversion for 'this' must be discarding cv-quals. */
+ inform (input_location, " passing %qT as %<this%> "
+ "argument discards qualifiers",
+ from);
+ else
+ inform (loc, " no known conversion for implicit "
+ "%<this%> parameter from %qT to %qT",
+ from, info->to_type);
+ }
+ else if (!TYPE_P (info->from))
+ {
+ if (info->n_arg >= 0)
+ inform (loc, " conversion of argument %d would be ill-formed:",
+ info->n_arg+1);
+ perform_implicit_conversion (info->to_type, info->from,
+ tf_warning_or_error);
+ }
else if (info->n_arg == -2)
/* Conversion of conversion function return value failed. */
inform (loc, " no known conversion from %qT to %qT",
- info->from_type, info->to_type);
+ from, info->to_type);
else
inform (loc, " no known conversion for argument %d from %qT to %qT",
- info->n_arg+1, info->from_type, info->to_type);
+ info->n_arg+1, from, info->to_type);
And too few spaces around '+'.
Also, are there other qualifiers of 'this' besides 'const'?
Cheers,
Manuel.
