Confusing claim about HashMap in no_std

[justinmoon]

This section claims the existence of a collections crate which can provide Vec and HashMap implementations.

I don't believe such a crate exists. Nothing comes up in crates.io. Vec is provided by alloc crate, but HashMap is not.

[cameronelliott]

It is worth noting this page says the reason HM is not available is due to a lack of a secure random number generator:
https://stackoverflow.com/a/65470850/86375

[therealprof]

That statement is not quite right. There's no collections crate but a collections module in alloc (re-exported in std). The fact that HashMap (and HashSet) are only available in std rather than alloc due to an implicit requirement of a random generator is annoying but maybe it would be better to simply refer to hashbrown for now instead of highlighting an internal detail which is really no help for a user desperately longing for HashMap?

[cameronelliott]

@therealprof did you by chance look at the PR I submitted? Maybe you have some suggestions or improvement ideas for another PR? It actually sounds like a good idea to mention Hashbrown in that section of the docs.

[therealprof]

I did have a look. I would recommend making two more changes:

• Change "collections crate" into e.g. "alloc::collections module"
• Turn the "** HashMap and HashSet are not available due to a lack of a secure random number generator." remrk into a regular text, recommending to look into hashbrown if a HashMap or HashSet collection type is needed.