See: https://eel.is/c++draft/unord.req#lib:max_load_factor,unordered_associative_containers_

There's no mention of how to handle a value of infinity.

This can have somewhat surprising effects in implementations.

For example, an implementation of reserve() might be as is literally specified in the standard:

    a.rehash(ceil(n / a.max_­load_­factor()))

This has the unfortunate caveat that for all positive values of n,  we're invoking `a.rehash(0)`.

This means that if `a.bucket_count() == 0`, `a.reserve(1000)` can legally be a no-op and 

`a.bucket_count() == 0` continues to hold. This can be observed in libc++: 

This seems to be a defect in wording as I assume the intention was that `reserve(n)` for some

positive n would allocate at least 1 bucket.

Implementations are free to ignore such values for the maximum load factor but they are not

required to.

I believe infinity should either become an invalid precondition for `max_load_factor(z)` or the

wording around reserve() should be updated so as to guide implementations how to handle

this value of maximum load factor.

- Christian