[Bug c++/64194] New: [C++14] <unresolved overloaded function type> for function template with auto return

[Bug c++/64194] New: [C++14] <unresolved overloaded function type> for function template with auto return

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

            Bug ID: 64194
           Summary: [C++14] <unresolved overloaded function type> for
                    function template with auto return
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org

template <typename Tp> auto id() { }

template <typename T> void g(T) { }

int main()
{
    // id<int>;
    g(id<int>);
}

G++ fails to resolve id<int> in the call.

over.cc: In function ‘int main()’:
over.cc:8:14: error: no matching function for call to ‘g(<unresolved overloaded
function type>)’
     g(id<int>);
              ^
over.cc:3:28: note: candidate: template<class T> void g(T)
 template <typename T> void g(T) { }
                            ^
over.cc:3:28: note:   template argument deduction/substitution failed:
over.cc:8:14: note:   couldn't deduce template parameter ‘T’
     g(id<int>);
              ^

It works if the reference to id<int> is uncommented, or if auto id() is changed
to void id()
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From: "bep684 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/64195] New: type_traits.h: is_trivially_copyable unimplemented
Date: Fri, 05 Dec 2014 15:39:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd195

            Bug ID: 64195
           Summary: type_traits.h: is_trivially_copyable unimplemented
           Product: gcc
           Version: 4.9.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bep684 at gmail dot com

Attempting to use std::is_trivially_copyable results in the following error at
compile-time:
"error: 'is_trivially_copyable' is not a member of 'std'"

Found the following line in type_traits.h:
"// is_trivially_copyable (still unimplemented)"

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

Ville Voutilainen <ville.voutilainen at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-12-08
                 CC|                            |ville.voutilainen at gmail dot com
     Ever confirmed|0                           |1

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |okannen at gmail dot com

--- Comment #10 from Patrick Palka <ppalka at gcc dot gnu.org> ---
*** Bug 96361 has been marked as a duplicate of this bug. ***

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ppalka at gcc dot gnu.org
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:2c58f5cadfac338a67723fd6e41c9097760c4a33

commit r11-2420-g2c58f5cadfac338a67723fd6e41c9097760c4a33
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Jul 29 22:06:44 2020 -0400

    c++: overload sets and placeholder return type [PR64194]

    In the testcase below, template argument deduction for the call
    g(id<int>) goes wrong because the functions in the overload set id<int>
    each have a yet-undeduced auto return type, and this undeduced return
    type makes try_one_overload fail to match up any of the overloads with
    g's parameter type, leading to g's template argument going undeduced and
    to the overload set going unresolved.

    This patch fixes this issue by performing return type deduction via
    instantiation before doing try_one_overload, in a manner similar to what
    resolve_address_of_overloaded_function does.

    gcc/cp/ChangeLog:

            PR c++/64194
            * pt.c (resolve_overloaded_unification): If the function
            template specialization has a placeholder return type,
            then instantiate it before attempting unification.

    gcc/testsuite/ChangeLog:

            PR c++/64194
            * g++.dg/cpp1y/auto-fn60.C: New test.

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |11.0
             Status|ASSIGNED                    |RESOLVED

--- Comment #12 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Should be fixed for GCC 11, thanks for the reports.

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |max.kanold@nu-cost.com

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
*** Bug 93317 has been marked as a duplicate of this bug. ***

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |janezz55 at gmail dot com

--- Comment #14 from Jonathan Wakely <redi at gcc dot gnu.org> ---
*** Bug 97778 has been marked as a duplicate of this bug. ***

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |leonid at volnitsky dot com

--- Comment #15 from Jonathan Wakely <redi at gcc dot gnu.org> ---
*** Bug 54111 has been marked as a duplicate of this bug. ***

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

--- Comment #16 from Jason Merrill <jason at gcc dot gnu.org> ---
The fix looks safe to backport; it isn't a regression, but the number of
duplicate reports argue for making an exception.

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

--- Comment #17 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:4fb1ee669ccaad16795baf25d2cab48d8cf8c1eb

commit r10-9136-g4fb1ee669ccaad16795baf25d2cab48d8cf8c1eb
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Jul 29 22:06:44 2020 -0400

    c++: overload sets and placeholder return type [PR64194]

    In the testcase below, template argument deduction for the call
    g(id<int>) goes wrong because the functions in the overload set id<int>
    each have a yet-undeduced auto return type, and this undeduced return
    type makes try_one_overload fail to match up any of the overloads with
    g's parameter type, leading to g's template argument going undeduced and
    to the overload set going unresolved.

    This patch fixes this issue by performing return type deduction via
    instantiation before doing try_one_overload, in a manner similar to what
    resolve_address_of_overloaded_function does.

    gcc/cp/ChangeLog:

            PR c++/64194
            * pt.c (resolve_overloaded_unification): If the function
            template specialization has a placeholder return type,
            then instantiate it before attempting unification.

    gcc/testsuite/ChangeLog:

            PR c++/64194
            * g++.dg/cpp1y/auto-fn60.C: New test.

    (cherry picked from commit 2c58f5cadfac338a67723fd6e41c9097760c4a33)

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.0                        |10.3

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |barry.revzin at gmail dot com

--- Comment #18 from Jonathan Wakely <redi at gcc dot gnu.org> ---
*** Bug 86826 has been marked as a duplicate of this bug. ***

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

--- Comment #19 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:9499fe0403e310f4eb1f23279bff84259e120e76

commit r9-9453-g9499fe0403e310f4eb1f23279bff84259e120e76
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Jul 29 22:06:44 2020 -0400

    c++: overload sets and placeholder return type [PR64194]

    In the testcase below, template argument deduction for the call
    g(id<int>) goes wrong because the functions in the overload set id<int>
    each have a yet-undeduced auto return type, and this undeduced return
    type makes try_one_overload fail to match up any of the overloads with
    g's parameter type, leading to g's template argument going undeduced and
    to the overload set going unresolved.

    This patch fixes this issue by performing return type deduction via
    instantiation before doing try_one_overload, in a manner similar to what
    resolve_address_of_overloaded_function does.

    gcc/cp/ChangeLog:

            PR c++/64194
            * pt.c (resolve_overloaded_unification): If the function
            template specialization has a placeholder return type,
            then instantiate it before attempting unification.

    gcc/testsuite/ChangeLog:

            PR c++/64194
            * g++.dg/cpp1y/auto-fn60.C: New test.

    (cherry picked from commit 2c58f5cadfac338a67723fd6e41c9097760c4a33)

[Bug c++/64194] [C++14] <unresolved overloaded function type> for function template with auto return

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64194

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |spartan_117 at juno dot com

--- Comment #20 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 97999 has been marked as a duplicate of this bug. ***