[Bug c++/96333] New: Regression on concepts constraint checking

[Bug c++/96333] New: Regression on concepts constraint checking

[joel.falcou at lri dot fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96333

            Bug ID: 96333
           Summary: Regression on concepts constraint checking
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: joel.falcou at lri dot fr
  Target Milestone: ---

The following code :

https://godbolt.org/z/ah6ssM

exhibits a regression so that not having const& on one of the g overload make
them ambiguous.

g++ 10.1 and clang 10 compiles both version without error.
The workaround to add const& is OK but I think this is not normal behavior.

[Bug c++/96333] Regression on concepts constraint checking

[barry.revzin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96333

Barry Revzin <barry.revzin at gmail dot com> changed:

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

--- Comment #1 from Barry Revzin <barry.revzin at gmail dot com> ---
Shorter repro:

template <typename T> int f(T );
template <typename T> requires true int f(T const&);

int i = f(42);

[Bug c++/96333] [10/11 Regression] Regression on concepts constraint checking

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96333

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |10.2.0, 11.0
            Summary|Regression on concepts      |[10/11 Regression]
                   |constraint checking         |Regression on concepts
                   |                            |constraint checking
      Known to work|                            |10.1.0
           Keywords|                            |needs-bisection,
                   |                            |rejects-valid
   Target Milestone|---                         |10.3

[Bug c++/96333] [10/11 Regression] Regression on concepts constraint checking

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96333

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|needs-bisection             |

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Started with r11-1571 and I think G++ is correct to reject it.

The second overload is not a more constrained version of the first, they're
just ambiguous.

[Bug c++/96333] [10/11 Regression] Regression on concepts constraint checking

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96333

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The commit is:

    c++: Refinements to "more constrained".

    P2113 from the last C++ meeting clarified that we only compare constraints
    on functions or function templates that have equivalent template parameters
    and function parameters.

And the relevant change is
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2113r0.html

[Bug c++/96333] [10/11 Regression] Regression on concepts constraint checking

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96333

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> ---
I agree with Jonathan's analysis.

[Bug c++/96333] [10/11 Regression] Regression on concepts constraint checking

[david at doublewise dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96333

David Stone <david at doublewise dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |david at doublewise dot net

--- Comment #5 from David Stone <david at doublewise dot net> ---
*** Bug 98987 has been marked as a duplicate of this bug. ***

[Bug c++/96333] [10/11 Regression] Regression on concepts constraint checking

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96333

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrei.popa105 at yahoo dot com

--- Comment #6 from Patrick Palka <ppalka at gcc dot gnu.org> ---
*** Bug 105111 has been marked as a duplicate of this bug. ***