The exposition-only type trait `pair-like` includes `ranges::subrange`,
but in every single case excludes `ranges::subrange` from the list. This
patch introduces two new traits `__tuple_like_no_subrange` and
`__pair_like_no_subrange`, which exclude `ranges::subrange` from the
possible matches. `__pair_like` is no longer required, and thus removed.
`__tuple_like` is implemented as `__tuple_like_no_subrange` or a
`ranges::subrange` specialization.
This has been done using the following command
find libcxx/test -type f -exec perl -pi -e 's|^([^/]+?)((?<!::)size_t)|\1std::\2|' \{} \;
And manually removed some false positives in std/depr/depr.c.headers.
The `std` module doesn't export `::size_t`, this is a preparation for that module.
Reviewed By: ldionne, #libc, EricWF, philnik
Differential Revision: https://reviews.llvm.org/D146088
`subrange` is also a `tuple-like`. To avoid the add entire `subrange` dependencies to `tuple-like`, we need forward declaration of `subrange`. However, the class template constraints of `subrange` currently requires `__iterator/concepts.h`, which requires `<concepts>`. The problem is that currently `tuple-like` is used in several different places, including libc++ extension for pair constructors. we don't want to add `<concepts>` to pair and other stuff. So this change also created several small headers that `subrange`'s declaration needed inside `__iterator/concepts/`
Differential Revision: https://reviews.llvm.org/D136268
