Add support for HashMap<T> and HashSet<T>

[metaproph3t]

reference implementation: snippet 1, snippet 2

[marcus-pousette]

Good that you created an issue for this. I have postponed the for a while. Are you working on a project that requires this feature? (and you can't get away with arrays)

[vantessel]

+1 on HashMap, nothing that can't be done in other ways but having native support for hash maps would definitely speed up things

[beautyfree]

+1