This patch adds `static_assert` using `is_class_v` and `is_union_v` to
reject no-class type template parameters.
Fixes#132133
---------
Co-authored-by: A. Jiang <de34@live.cn>
This pull request implements LWG3984: ranges::to's recursion branch
may be ill-formed.
In the current implementation, ranges::to's recursion branch pipes the
range into a `views::transform(/* lambda */)`, which is a __range_adaptor_closure
object. In libc++, the pipe operator of __range_adaptor_closure requires a
viewable_range, so the following code won't compile, as the type of lvalue
`r` doesn't model viewable_range:
#include <ranges>
#include <vector>
#include <list>
int main() {
std::vector<std::vector<int>> v;
auto r = std::views::all(std::move(v));
auto l = std::ranges::to<std::list<std::list<int>>>(r);
}
Co-authored-by: A. Jiang <de34@live.cn>
## Abstract
This pull request converts the `operator()` of all CPOs and niebloids
related to C++23 ranges to `static`.
## Motivation
In `libc++`, CPOs and niebloids are implemented as function objects.
Currently, the `operator()` for such a function object is a
`const`-qualified member function. This means that even if the function
object is has no data members, an extra register is used to pass in the
`this` pointer when calling `operator()`, unless the compiler can inline
the function call. Declaraing `operator()` as `static` would optimize
away the unnecessary `this` pointer passing for stateless function
objects, since there is no object instance state that needs to be
accessed.
## Reference
- [P1169R4: static `operator()`](https://wg21.link/P1169R4)
This updates the clang-format we use in libc++ to 17. This is necessary
to start running the generated-files checks in GitHub Actions (in
#68920). In fact this is a pre-existing issue regardless of #68920 --
right now our ignore_format.txt job disagrees with the LLVM-wide
clang-format job.
Since LLVM 17 has been branched and is on the verge of being released,
we can drop the CI job that tests against Clang 15. I think the number
of cherry-picks to `release/17.x` will be a lot smaller now, so keeping
a Clang 15 job around for that purpose seems unnecessary.
As a fly-by, this patch also removes some Clang 15 workarounds and test
suite annotations as we usually do. It also removes some slightly older
gcc test suite annotations that were missed.
