[Bug c++/84920] New: Better handling of unmatched/ambiguous calls

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84920

            Bug ID: 84920
           Summary: Better handling of unmatched/ambiguous calls
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dmalcolm at gcc dot gnu.org
  Target Milestone: ---

As reported by user "jcoffland" on Hacker News:
https://news.ycombinator.com/item?id=16598071

> One improvement I'd like to see is a simplified error message
> for mismatched overloaded calls. If you make an overloaded call
> for which the is no matching conversion or if the conversation is
> ambiguous the compiler will "helpfully" dump a list of possibly
> matching overloaded function signatures. The list can be hundreds
> of lines long.
>
> For example, when you try to pipe a class to std::cout that
> doesn't have an std::ostream &operator<<(std::ostream &, const X &).
> Perhaps instead of dumping the complete function signatures it
> could show one function signature followed by a list of types
> accepted as the second parameter. Since the signatures are
> otherwise the same. Such improvements could also reduce
> template error spew.

I hope to have a look at this in the GCC 9 timeframe, so filing this here.