I recently looked at `std::unordered_map` and noticed a bit of a
bizarre handling of `std::hash` in the standard library.
Why of all types that could be useful, does the standard define only
`std::vector<bool>`?
Where `std::tuple` or other vectors are left unusable.

What is the reason for standard not defining
`std::hash<std::vector<T>>` if `T` has a hash?
And why is `bool` the only exception there? What was the motivation for this?
https://eel.is/c++draft/vector.bool#pspc-7