Some types that inherit from `view_interface` do not meet the
preconditions. This came up during discussion
in https://reviews.llvm.org/D112631. Currently, the behavior is IFNDR,
but the preconditions can be easily checked, so let's do so.
In particular, we know each public member function calls the
`__derived()` private function, so we can do the check there. We
intentionally do it as a `static_assert` instead of a `requires` clause
to avoid hard erroring in some cases, such as with incomplete types. An
example hard error is:
```
llvm-project/build/include/c++/v1/__ranges/view_interface.h:48:14: note: because 'sizeof(_Tp)' would be invalid: invalid application of 'sizeof' to an incomplete type 'MoveOnlyForwardRange'
requires { sizeof(_Tp); } &&
^
llvm-project/build/include/c++/v1/__ranges/view_interface.h:73:26: error: no matching member function for call to '__derived'
return ranges::begin(__derived()) == ranges::end(__derived());
^~~~~~~~~
llvm-project/libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp:187:31: note: in instantiation of function template specialization 'std::ranges::view_interface<MoveOnlyForwardRange>::empty<Mov
eOnlyForwardRange>' requested here
assert(!std::move(moveOnly).empty());
```
Reviewed By: Quuxplusone, Mordante, #libc
Differential Revision: https://reviews.llvm.org/D112665
We've been forgetting to add those to most of the <ranges> review.
To avoid forgetting in the future, I added an item in the pre-commit
checklist.
Differential Revision: https://reviews.llvm.org/D106287
This has been broken out of D104170 since it should be merged whether or
not we go ahead with the module map changes.
Differential Revision: https://reviews.llvm.org/D104175
Joe Loser