[Bug c++/113303] New: One can assign to const reference in a template partial specialization

[fchelnokov at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113303

            Bug ID: 113303
           Summary: One can assign to const reference in a template
                    partial specialization
           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: ---

This program


template <auto &>
struct A;

template <const auto & a>
struct A<a>{
  A() { a = 1; }
};

int x = 0;
A<x> s;


is erroneously accepted by GCC despite the assignment to const reference.

Clang complains that "class template partial specialization is not more
specialized than the primary template".

And MSVC allows the specialization, but "you cannot assign to a variable that
is const"

Online demo: https://godbolt.org/z/1aPK8K311