linux-kernel - Re: [PATCH v1 1/2] rust: time: Rename Delta's methods as_micros_ceil and as

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Message-ID: <CANiq72kHvfkrK0KG2Y60HkLMt=mgJrJMOcuF9Feker0FjgoVkg@mail.gmail.com>
Date: Thu, 19 Jun 2025 13:44:52 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: FUJITA Tomonori <fujita.tomonori@...il.com>, aliceryhl@...gle.com, alex.gaynor@...il.com, 
	ojeda@...nel.org, anna-maria@...utronix.de, bjorn3_gh@...tonmail.com, 
	boqun.feng@...il.com, dakr@...nel.org, frederic@...nel.org, gary@...yguo.net, 
	jstultz@...gle.com, linux-kernel@...r.kernel.org, lossin@...nel.org, 
	lyude@...hat.com, rust-for-linux@...r.kernel.org, sboyd@...nel.org, 
	tglx@...utronix.de, tmgross@...ch.edu
Subject: Re: [PATCH v1 1/2] rust: time: Rename Delta's methods as_micros_ceil
 and as_millis

On Thu, Jun 19, 2025 at 11:28 AM Andreas Hindborg <a.hindborg@...nel.org> wrote:
>
> 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.

It is an integer division by compile-time constant, so likely just a
multiplication and some adjustment, so it depends on whether we
consider that "expensive".

However, even if we consider that "expensive", we will still have the
same question when we have a really cheap method.

The root issue is that the table just doesn't say what to do in some
of the "free" cases, and it is generally confusing.

Since I am asking for opinions: why do you consider `as_*` as
expecting to borrow? The standard does take `&self` the majority of
the time (but not always), and Clippy also expects a borrow, but you
also said in a previous iteration that you don't want to take a
pointer just to pass an integer, which makes sense: we wouldn't pass a
reference if we were using the integer.

Thanks!

(I am tempted to propose a new table...)

Cheers,
Miguel