Clang accepts constraint mismatch at argument in template parameter-list

[llvmbot]

Bugzilla Link	49841
Version	trunk
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@zygoloid

Extended Description

https://godbolt.org/z/vf3Gn5hTK

#include <concepts>

template <std::signed_integral>
struct A {};

template <template <std::integral> typename>
struct B {};

B<A> b;

clang accepts it.

[ahatanaka]

clang rejects the code if I pass -frelaxed-template-template-args to the command line:

error: template template argument 'A' is more constrained than template template parameter ''

[ahatanaka]

https://reviews.llvm.org/D109496 deprecated -frelaxed-template-template-args, but the patch was reverted later.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (llvmbot)

| | | | --- | --- | | Bugzilla Link | [49841](https://llvm.org/bz49841) | | Version | trunk | | OS | All | | Reporter | LLVM Bugzilla Contributor | | CC | @zygoloid |

Extended Description

https://godbolt.org/z/vf3Gn5hTK

#include <concepts>

template <std::signed_integral>
struct A {};

template <template <std::integral> typename>
struct B {};

B<A> b;

clang accepts it.

[shafik]

@fahadnayyar any progress here?

[mizvekov]

Duplicate of #36505