"Convert `as X` to `X::from`" assist

[SludgePhD]

It would be useful if rust-analyzer had an assist that allows quickly changing an as x cast to an x::from-style cast (when the appropriate From impl exists). This would save a bunch of typing when refactoring casts to be more precise (since as _ will wrap).

Additionally, it could also offer a conversion to .try_into().unwrap() when there is only a TryFrom/TryInto impl but no From/Into impl, since that's a common change too.

[benodiwal]

@ShoyuVanilla @ChayimFriedman2 I have raised a PR for this issue. Thanks !

[ChayimFriedman2]

@benodiwal It is not clear that we want to accept new assists currently, or this assist at all. While creating a PR is fine, it'd be better (for you, to not waste work) if you would've discussed with team members whether we want that instead of jumping to implementing it.

[benodiwal]

Got it, I’ll be careful about this going forward.