[Bug c++/100472] New: [C++17] Wrong template non-type argument handling on function reference to noexcept functions

[Bug c++/100472] New: [C++17] Wrong template non-type argument handling on function reference to noexcept functions

[frankhb1989 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100472

            Bug ID: 100472
           Summary: [C++17] Wrong template non-type argument handling on
                    function reference to noexcept functions
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: frankhb1989 at gmail dot com
  Target Milestone: ---

Case:

template<void(&)()>
void h()
{}

void f() noexcept
{}

int main()
{
        h<f>();
}

g++ prog.cc -Wall -Wextra -std=c++17 

prog.cc: In function 'int main()':
prog.cc:10:7: error: no matching function for call to 'h<f>()'
   10 |  h<f>();
      |       ^
prog.cc:2:6: note: candidate: 'template<void (& <anonymous>)()> void h()'
    2 | void h()
      |      ^
prog.cc:2:6: note:   template argument deduction/substitution failed:
prog.cc:10:7: error: '(void (&)())f' is not a valid template argument for type
'void (&)()'
   10 |  h<f>();
      |       ^
prog.cc:10:7: note: it must be the name of a function with external linkage

Removing `noexcept` makes all errors disappeared. So, the real failure is from
the initialization of the template non-type parameter. This should not fail as
per the rules in [temp.arg.nontype], [dcl.init.ref] and [expr.const] (see also
N4268). Even if the conversion should have been failed, the last diagnostic
message is clearly wrong and confusing. This message comes from the conversion
performed on the template non-type argument as I see in
convert_nontype_argument_function in pt.c, and it should not occur since the
[temp.arg.nontype] changes in C++11.

[Bug c++/100472] [C++17] Wrong template non-type argument handling on function reference to noexcept functions

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100472

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |ppalka at gcc dot gnu.org
         Resolution|---                         |DUPLICATE

--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Dup of PR97420

*** This bug has been marked as a duplicate of bug 97420 ***