[Bug c++/95073] New: Add "did you mean" when fn declaration could be found via ADL

["mpolacek at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95073

            Bug ID: 95073
           Summary: Add "did you mean" when fn declaration could be found
                    via ADL
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

namespace N {
  struct X { };
  void f(X);
}

void
g ()
{
  extern void f(); // #1
  N::X x;
  f(x); // calls locally declared function #1, no ADL
}

we issue

q.C: In function ‘void g()’:
q.C:11:6: error: too many arguments to function ‘void f()’
   11 |   f(x);
      |      ^
q.C:9:15: note: declared here
    9 |   extern void f();
      |               ^

but we could do better and say

q.C:11:3: error: too many arguments to function call, expected 0, have 1; did
you mean 'N::f'?
  f(x);
  ^
  N::f
q.C:3:8: note: 'N::f' declared here
  void f(X);
       ^