As per discussion on IRC. I am about to file an RFC for further
discussion about the more general issue of whether to enforce
invariants through types, typestate, or dynamic checks, but for now,
removing the misleading name "last_unsafe".
This required changing almost all users of hashmaps to import the hashmap interface first.
The `size` member in the hashmap structure was renamed to `count` to work around a name conflict.
This required changing almost all users of hashmaps to import the hashmap interface first.
The `size` member in the hashmap structure was renamed to `count` to work around a name conflict.
