Behavior change in 1.89

[Guara92]

Hi,

I noticed a change of behavior in clippy 1.89, I don't know if it's a bug or if I'm missing something of the new release, I have a small project to show the behavior change, this is my main.rs:

fn main() {
    let nums: Vec<i32> = ["1", "2", "whee!"].iter().flat_map(|x| x.parse().ok()).collect();
    println!("{:?}", nums);
}

I have this rust_toolchain.toml:

[toolchain]
channel = "1.88.0"

when I run cargo clippy I get this expected output:

error: variables can be used directly in the `format!` string
 --> src/main.rs:3:5
  |
3 |     println!("{:?}", nums);
  |     ^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
  = note: `-D clippy::uninlined-format-args` implied by `-D warnings`
  = help: to override `-D warnings` add `#[allow(clippy::uninlined_format_args)]`
help: change this to
  |
3 -     println!("{:?}", nums);
3 +     println!("{nums:?}");
  |

error: could not compile `clippy_errors` (bin "clippy_errors") due to 1 previous error
 --> src/main.rs:8:5
  |
8 |     return 2;
  |     ^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_return
  = note: `#[warn(clippy::needless_return)]` on by default
help: remove `return`
  |
8 -     return 2;
8 +     2
  |

warning: `clippy_errors` (bin "clippy_errors") generated 3 warnings (run `cargo clippy --fix --bin "clippy_errors"` to apply 2 suggestions)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.04s

If I bump the rust toolchain channel to 1.89.0, I don't get the lint triggered.

From what I see from the 1.89.0 doc the lint should still be a style warning https://rust-lang.github.io/rust-clippy/rust-1.89.0/index.html#uninlined_format_args
as in 1.88.0, I noticed that on master the lint is changed to pedantic allow, there is some misalignment between the doc and the actual code?

[flip1995]

Ah, I understand what happened: We backported the move to pedantic in rust-lang/rust#144742, so that the backport gets into stable a release early, because people were really annoyed by us moving that to warn-by-default in 1.88.0. But such lint move backports are not reflected in our docs. There's no easy fix for addressing this, without making the backporting process way more complicated. Since I have to do the backports, I for now just say "it is what it is".

Sorry for the inconvenience of the docs not matching reality :/

[flip1995]

This should've been in the 1.89 changelog, but sadly we missed that. I opened #15534 to include this info in the changelog.