[Bug c++/67138] New: [concepts] bogus "not more constrained" error for more constrained partial specialization

[eric.niebler at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67138

            Bug ID: 67138
           Summary: [concepts] bogus "not more constrained" error for more
                    constrained partial specialization
           Product: gcc
           Version: c++-concepts
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: eric.niebler at gmail dot com
  Target Milestone: ---

template <class T>
concept bool _Auto = true;

template <_Auto T>
struct test {};

template <_Auto T>
  requires requires (T t) { t + t; }
struct test<T> {};


yields:

test.cpp:10:8: error: partial specialization ‘struct test<T>’ does not
specialize any template arguments and is not more constrained than
 struct test<T> {};
        ^
test.cpp:6:8: note: primary template here
 struct test {};
        ^