[Bug c++/91133] [8/9/10/11 Regression] Wrong "partial specialization is not more specialized than" error

[Bug c++/91133] [8/9/10/11 Regression] Wrong "partial specialization is not more specialized than" error

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91133

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

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

[Bug c++/91133] [8/9/10/11 Regression] Wrong "partial specialization is not more specialized than" error

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91133

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> ---
This is really a question of partial ordering; determining whether the partial
specialization is more specialized than the primary class template is
equivalent to this testcase:

template<typename T> struct Id { typedef T type; };
template<typename T, typename U, U X> struct A {};

template<typename T, typename U, U X>        void f(A<T, U,   X>); // #1
template<typename T, typename Id<T>::type X> void f(A<T, int, X>); // #2

int main()
{
  f(A<int,int,42>()); // is #2 more specialized?
}

This was rejected as ambiguous by GCC going back at least to 4.1.  It is also
rejected by EDG/icc.  It is accepted by clang and msvc, like the original
testcase.

The issue is with the partial ordering deduction of #1 from #2: we deduce int
for U from the second argument, and Id<T>::type for U from the third argument,
and those don't agree, so deduction for the third argument fails in both
directions, and the functions are ambiguous.

This is related to open core issues 455 and 1337.

I don't know what rationale clang/msvc are using to conclude that #2 is more
specialized.

[Bug c++/91133] [9/10/11/12 Regression] Wrong "partial specialization is not more specialized than" error

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91133

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|8.5                         |9.4

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 8 branch is being closed.

[Bug c++/91133] [9/10/11/12 Regression] Wrong "partial specialization is not more specialized than" error

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91133

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|9.4                         |9.5

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9.4 is being released, retargeting bugs to GCC 9.5.

[Bug c++/91133] [10/11/12/13 Regression] Wrong "partial specialization is not more specialized than" error

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91133

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|9.5                         |10.4

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9 branch is being closed

[Bug c++/91133] [10/11/12/13 Regression] Wrong "partial specialization is not more specialized than" error

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91133

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.4                        |10.5

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 10.4 is being released, retargeting bugs to GCC 10.5.

[Bug c++/91133] [10/11/12/13 Regression] Wrong "partial specialization is not more specialized than" error

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91133

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |SUSPENDED
           Assignee|jason at gcc dot gnu.org           |unassigned at gcc dot gnu.org

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> ---
The error was downgraded to a pedwarn in r12-8256.  I still think it is
correct, but I'm suspending rather than closing due to the continuing
implementation divergence.

[Bug c++/91133] [11/12/13/14 Regression] Wrong "partial specialization is not more specialized than" error

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91133

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.