Those were found while trying to enable configurations like no-threads
and no-localization with Clang modules enabled.
Differential Revision: https://reviews.llvm.org/D153977
These concepts are used to ensure valid iterators are passed to PSTL algorithms, but can also be used for other interfaces.
Reviewed By: ldionne, #libc
Spies: EricWF, libcxx-commits
Differential Revision: https://reviews.llvm.org/D150493