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From: "fchelnokov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/112775] New: Class template partial specialization with
 decltype(n) is wrongly rejected
Date: Thu, 30 Nov 2023 09:27:22 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 13.2.1
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112775

            Bug ID: 112775
           Summary: Class template partial specialization with decltype(n)
                    is wrongly rejected
           Product: gcc
           Version: 13.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

In this program


template <class T, T, T>
class A;

template <auto n>
class A<decltype(n), n, n> {};


class template A has one type parameter T, and two arbitrary non-type
parameters (of type T). And also a specialization of A is provided, having
equal non-type template parameters.

The program is accepted by Clang and MSVC, but not by GCC:

error: partial specialization 'class A<decltype (n), n, n>' is not more
specialized than
    5 | class A<decltype(n), n, n> {};
      |       ^~~~~~~~~~~~~~~~~~~~
note: primary template 'template<class T, T <anonymous>, T <anonymous> > cl=
ass
A'

Online demo: https://godbolt.org/z/qjYMn8bd6=