Inconsistent parameter names for erase members of unordered containers

[jwakely]

The associative containers and the flat maps and sets all have:

    constexpr size_type erase(const key_type& x);
    template<class K> constexpr size_type erase(K&& x);

But the unordered containers have k and x for the same functions:

    constexpr size_type erase(const key_type& k);
    template<class K> constexpr size_type erase(K&& x);

This seems unnecessarily inconsistent. Either the unordered should use k for both (to be locally consistent), or use x for both (to be globally consistent).

[jwakely]

The unordered containers use k for nearly all keys, e.g. in find and count and contains etc. etc.
The only exceptions are one of the erase overloads, and both extract overloads.

So I suggest that erase(K&& x) should change to erase(K&& k). And maybe extract(const key_type& x) and extract(K&& x should change as well.