[libcxx][test] view_interface need not derive from view_base

[CaseyCarter]

Summary

... after LWG-3549.

[• Quuxplusone]

libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp

34–35

This is late-breaking C++20, right?
If so, just delete this line (and the following blank line): there's no point testing something that we (1) shouldn't do and (2) presumably plan to change.

[CaseyCarter]

Review comment.

[Mordante]

LGTM!

[jloser]

libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp

34–35

I'd prefer one of two different options:

1. Make this LIBCPP_STATIC_ASSERT as the current view_interface class template does indeed inherit from view_base.
2. Implement LWG3549 and make it so that view_interface class template no longer derives from view_base and then kill this line in the test as you've done.

Any appetite for implementing LWG3549? If not, I volunteer.

[• Quuxplusone]

libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp

34–35

Any appetite for implementing LWG3549? If not, I volunteer.

I suspect I speak for us all when I say: go for it! :)
(I still don't think that ought to block Casey's landing this one-line PR, though, so I'm being the second libc++ accepter.)

[CaseyCarter]

libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp

34–35

I'm not interested in implementing LWG3549 (for a second time =)), I'm only motivated to have the test not apply non-standard requirements when stdlib=msvc. How about if we split the work: I'll remove this test line, and you can implement LWG3549?

[Mordante]

libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp

34–35

It would be great when you implement LWG3549 @jloser!
I agree LWG3549 shouldn't block landing this commit.

[jloser]

libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp

34–35

@CaseyCarter seems reasonable! https://reviews.llvm.org/D117714 is almost done for implementing LWG3539.

libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp

 struct Empty { };
 
 static_assert(!ValidViewInterfaceType<void>);
 static_assert(!ValidViewInterfaceType<void*>);
 static_assert(!ValidViewInterfaceType<Empty*>);
 static_assert(!ValidViewInterfaceType<Empty const>);
 static_assert(!ValidViewInterfaceType<Empty &>);
 static_assert( ValidViewInterfaceType<Empty>);
 
-static_assert(std::derived_from<std::ranges::view_interface<Empty>, std::ranges::view_base>);
-
 using InputIter = cpp20_input_iterator<const int*>;
 
 struct InputRange : std::ranges::view_interface<InputRange> {
   int buff[8] = {0, 1, 2, 3, 4, 5, 6, 7};
   constexpr InputIter begin() const { return InputIter(buff); }
   constexpr InputIter end() const { return InputIter(buff + 8); }
 };
 
 struct NotSizedSentinel {