Cannot understand this error: HashMap::Keys::rev()

[worik]

@H2CO3

What is not comprehensible about that, in particular?

Pretty much everything.

@H2CO3

HashMap's iterator is not reversible. The reason for that is that iteration over a hash map happens in random order, so it doesn't make sense to "reverse" it

True. I meant to sort the Keys (only can be done on nightly be the looks)

But the documentation has rev