These headers have become very small by using compiler builtins, often
containing only two declarations. This merges these headers, since
there doesn't seem to be much of a benefit keeping them separate.
Specifically, `is_{,_nothrow,_trivially}{assignable,constructible}` are
kept and the `copy`, `move` and `default` versions of these type traits
are moved in to the respective headers.
Found while running libc++'s test suite with MSVC's STL.
* I've filed [LWG-4021](https://cplusplus.github.io/LWG/issue4021)
"`mdspan::is_always_meow()` should be `noexcept`" and implemented this
in libc++'s product and test code.
* Use `LIBCPP_STATIC_ASSERT` to avoid issues with `noexcept`
strengthening in MSVC's STL.
+ As permitted by the Standard, MSVC's STL conditionally strengthens
`mdspan` construction/`is_meow`/`stride` and `elements_view` iterator
`base() &&`, and always strengthens `basic_stringbuf` `swap`.
+ In `mdspan/properties.pass.cpp`, this also upgrades runtime `assert`s
to `static_assert`s.
* Improvement: Upgrade `assert` to `static_assert` when inspecting the
`noexcept`ness of `std::ranges::iter_move`. (These `!noexcept` tests
weren't causing issues for MSVC's STL, so I didn't change them to be
libc++-specific.)
Fixes uglification in mdspan deduction guides, which CI
did not test for until recently. The CI modification
and mdspan testing overlapped, so mdspan landed with green
CI, and the CI modification landed too.
Make most assertions in mdspan and its helper classes
trigger during a hardened build in order to catch
out of bounds access errors.
Also moves all mdspan assertions tests from libcxx/test/std
to libcxx/test/libcxx.
Differential Revision: https://reviews.llvm.org/156181
This implements P0009 std::mdspan ((https://wg21.link/p0009)),
a multidimensional span with customization points for
layouts and data access.
Co-authored-by: Damien L-G <dalg24@gmail.com>
Differential Revision: https://reviews.llvm.org/154367
