Re: [PATCH v4 2/7] rust: types: introduce ForLt base trait for CovariantForLt

[Miguel Ojeda]

On Sat, Jun 27, 2026 at 3:51 PM Danilo Krummrich <dakr@xxxxxxxxxx> wrote:
>
> The only way this could silently break would be to use ForLt!(), but then don't
> use the explicitly provided safe cast_ref() method, and instead open-code it
> with an unsafe transmute() assuming covariance from ForLt!().

Yeah, that is the not-compile-error case I was considering.

i.e. I was trying to think if there could be an issue with the name
reuse, since it can always be a pitfall. For in-tree I agree it isn't
a problem. For out-of-tree users, given it is very new and it is
unlikely they had that case, I think it is also fine.

(But e.g. if it were something that had been there for a long time,
e.g. in an LTS already, then I would say it would have been better to
pick another name).

> I can add them on apply, or we leave them as good first issue, as you prefer.

Up to you! I didn't want to add noise/nit work, but if it is fixed
already, then that is great.

[ I also saw some non-Markdown comments in the other commits, e.g.

    // Invariant ForLt types (e.g. containing a Mutex)

  in the sample. ]

Thanks!

Cheers,
Miguel