rand: re-export UnwrapMut & UnwrapErr

[baloo]

• Added a CHANGELOG.md entry

Summary

Motivation

Consumers may not directly depend on rand_core and those unwrap wrappers may be convenient.

Details

[vks]

Do you have a use case where this is convenient?

[newpavlov]

I think that use of these wrappers should be rare enough in practice to warrant a minor pain of importing them as rand::rand_core::{UnwrapMut, UnwapErr}'.

[baloo]

I'm not using it, that was just following up on this comment:
#1593 (review)

[dhardy]

I think that use of these wrappers should be rare enough in practice to warrant a minor pain of importing them as rand::rand_core::{UnwrapMut, UnwapErr}'.

We don't have (pub) rand::rand_core, because most parts which aren't implementation helpers are already re-export from rand, however on examination we're also missing:

• OsError (though this is available as <OsRng as TryRngCore>::Error)
• RngReadAdapter

All of these are things which might be rarely used. I think the best thing may be to just export the three adapters from rand and the error type from rand::rngs.

[newpavlov]

We don't have (pub) rand::rand_core, because most parts which aren't implementation helpers are already re-export from rand

Huh... I missed that. I think it's better to simply re-export rand_core. There are virtually no drawbacks to doing that (the only thing I could think of is an additional entry in docs, but here you propose to create several such entries), while not having access to rand_core from rand creates headaches like this.

[baloo]

I agree with the idea rand should re-export rand_core. Here is a PR for that: #1604 up for you to choose.