Re: [PATCH v1 1/2] rust: time: Rename Delta's methods as_micros_ceil and as_millis

[Andreas Hindborg <a.hindborg@kernel.org>]

"Miguel Ojeda" <miguel.ojeda.sandonis@gmail.com> writes:

> On Thu, Jun 19, 2025 at 9:08 AM FUJITA Tomonori
> <fujita.tomonori@gmail.com> wrote:
>>
>> So would the function be defined like this?
>>
>> fn as_nanos(self) -> i64;
>>
>> If that's the case, then we've come full circle back to the original
>> problem; Clippy warns against using as_* names for trait methods that
>> take self as follows:
>>
>> warning: methods called `as_*` usually take `self` by reference or `self` by mutable reference
>
> Yeah, the Clippy warning is indeed one more data point that the
> guidelines are confusing to the point of having Clippy complain or,
> more likely, the guidelines' intention is that we should just pick
> `&self`.
>
> If we decide to be OK with `self`s in the kernel for these cases, we
> can simply disable the lint. Doing so means we lose the rest of the
> checking for that lint, sadly.
>
> And, yeah, we are indeed going in circles.
>
> What I would normally suggest for cases like this is answering: what
> would be the best for the kernel's particular case, regardless of
> existing guidelines/lints? Then, if we think it is better to be
> different, and there is enough justification to do so, then try to
> mitigate the lose of the lints, talk to upstream, write our own
> variation of the guidelines, etc.
>
> So I would like to hear if anybody feels strongly about either
> direction, i.e. any other pros/cons that we haven't thought of.

The table at [1] seems to suggest `to_*` or `into_*` being the right
prefix for this situation. It does not fully match `to_*`, as the
conversion is not expensive. It does not match `into_*` as the type is
`Copy`.

I am leaning towards `to_*`, but no strong feelings against `into_*`.

I would not go with `as_*`, I would expect that to borrow.


Best regards,
Andreas Hindborg