Clippy suggests an unstable attribute instead of a deprecated one for #[cfg_attr(rustfmt, rustfmt_skip)]

[stephanemagnenat]

I'm disabling rustfmt for some lines of my code because I have functions with multiple arguments and for the sake of exposing the logical reasoning of the algorithm, I want to group them on multiple lines. Therefore, I am using:

#[cfg_attr(rustfmt, rustfmt_skip)]
...

Running cargo clippy tells me:

`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes
...
help: use: `#[rustfmt::skip]`

However, if I replace these with #[rustfmt::skip], I'm getting the following error:

error[E0658]: attributes on expressions are experimental
...
note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information

I assume it is a bug for a tool in stable Rust to suggest to use an experimental code to replace valid (although deprecated) code.

Meta

rustc --version --verbose:

rustc 1.53.0 (53cb7b09b 2021-06-17)
binary: rustc
commit-hash: 53cb7b09b00cbea8754ffb78e7e3cb521cb8af4b
commit-date: 2021-06-17
host: x86_64-unknown-linux-gnu
release: 1.53.0
LLVM version: 12.0.1

[ibraheemdev]

The attribute is not unstable, attributes are just not supported on expressions. You can put #[rustfmt::skip] on the outer function. I don't think this is a bug.

[stephanemagnenat]

I see, but #[cfg_attr(rustfmt, rustfmt_skip)] does work on expressions. So in that sense, it is a regression (shrinking) of the feature-set, isn't it?

[fmease]

In the future, please report Clippy-specific issues over at https://github.com/rust-lang/rust-clippy.

[fmease]

Could you provide a concrete reproducer? The ...s from the issue description are way too vague.

For example, let _ = #[cfg_attr(…)] 0; isn't a reproducer since it leads to an error and #[cfg_attr(...)] 0; (on a statement expression) isn't one either because it compiles with cfg_attr and with rustfmt::skip.

[stephanemagnenat]

Sorry for reporting to the wrong place.

This issue can be reproduced by commenting the line 44 of this file (after cloning the repository and before running clippy on it).