linux-kernel - Re: [PATCH] rust: disable `clippy::needless

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Message-ID: <Z_0XKfAMnWElZDzU@google.com>
Date: Mon, 14 Apr 2025 14:09:45 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, Tamir Duberstein <tamird@...il.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH] rust: disable `clippy::needless_continue`

On Thu, Apr 03, 2025 at 06:38:05PM +0200, Miguel Ojeda wrote:
> Starting with Rust 1.86.0, Clippy's `needless_continue` lint complains
> about the last statement of a loop [1], including cases like:
> 
>     while ... {
>         match ... {
>             ... if ... => {
>                 ...
>                 return ...;
>             }
>             _ => continue,
>         }
>     }
> 
> as well as nested `match`es in a loop.
> 
> One solution is changing `continue` for `()` [2], but arguably using
> `continue` shows the intent better when it is alone in an arm like that.
> 
> Moreover, I am not sure we want to force people to try to find other
> ways to write the code either, in cases when that applies.
> 
> In addition, the help text does not really apply in the new cases the
> lint has introduced, e.g. here one cannot simply "drop" the expression:
> 
>     warning: this `continue` expression is redundant
>       --> rust/macros/helpers.rs:85:18
>        |
>     85 |             _ => continue,
>        |                  ^^^^^^^^
>        |
>        = help: consider dropping the `continue` expression
>        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_continue
>        = note: requested on the command line with `-W clippy::needless-continue`
> 
> The examples in the documentation do not show a case like this, either,
> so the second "help" line does not help.
> 
> In addition, locally disabling the lint is not possible with `expect`,
> since the behavior differs across versions. Using `allow` would be
> possible, but, even then, an extra line just for this is a bit too much,
> especially if there are other ways to satisfy the lint.
> 
> Finally, the lint is still in the "pedantic" category and disabled by
> default by Clippy.
> 
> Thus disable the lint, at least for the time being.
> 
> Feedback was submitted to upstream Clippy, in case this can be improved
> or perhaps the lint split into several [3].
> 
> Link: https://github.com/rust-lang/rust-clippy/pull/13891 [1]
> Link: https://lore.kernel.org/rust-for-linux/20250401221205.52381-1-ojeda@kernel.org/ [2]
> Link: https://github.com/rust-lang/rust-clippy/issues/14536 [3]
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>