It seems assumed that a `size_t` value can be passed to an allocator's `allocate` member function per the simple-allocator exposition-only concept in [allocator.requirements.general] and the minimal constraints for allocator types in [container.reqmts].

However, it is not exactly required that a type meeting the Cpp17Allocator requirements can be used with `size_t` values, because only allocator_traits<A>::size_type, which is possibly not `size_t`, is required to be usable with the allocator.

Do we want to change these constraints, or change the Cpp17Allocator requirements to require accepting `size_t` values?