`rustfmt::skip` sometimes ignored when using `error_on_line_overflow` and `error_on_unformatted`

[ilyvion]

Summary

I tried to format this code:

impl Blah {
    #[rustfmt::skip]
    fn foo() {
        {
            {
                select! {
                    _ = bar() => {
                        info!(
                            "WebAuthn challenge cache cleanup: __ registration, __ login, __ 2FA, __ email-change entries remaining",
                        );
                    },
                }
            }
        }
    }
}

(I tried to make it as small as possible without making the error go away)

Expected behavior

I expected to see this happen: Since I have rustfmt::skip, rustfmt should not concern itself with this function.

Actual behavior

Instead, this happened:

❯ rustup run nightly -- rustfmt foo.rs 
error[internal]: line formatted, but exceeded maximum width (maximum: 100 (see `max_width` option), found: 133)
 --> /home/alex/Documents/Projects/foo.rs:9:9:101
  |
9 | ...                   "WebAuthn challenge cache cleanup: __ registration, __ login, __ 2FA, __ email-change entries remaining",
  |                                                                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: set `error_on_unformatted = false` to suppress the warning against comments or string literals

Configuration

rustfmt configuration file (e.g. rustfmt.toml, if applicable):

edition = "2024"
error_on_line_overflow = true
error_on_unformatted = true

Reproduction Steps

Run rustfmt on the code above with the configuration above.

Meta

rustfmt --version:

rustfmt 1.9.0-nightly (bd08c9e718 2026-06-25)

[ilyvion]

It does work when I put #[rustfmt::skip] on the impl block itself, so that's a workaround I can use, but I still feel like this is a bug, because ideally I'd be able to put it on the info!() itself so the skipping has the least amount of impact on the surrounding code.

It becomes almost comical that the error still triggers when you try it on this absurd code:

impl Blah {
    #[rustfmt::skip]
    fn foo() {
        #[rustfmt::skip]
        {
            #[rustfmt::skip]
            {
                #[rustfmt::skip]
                select! {
                    #[rustfmt::skip]
                    _ = bar() => {
                        #[rustfmt::skip]
                        info!(
                            #[rustfmt::skip]
                            "WebAuthn challenge cache cleanup: __ registration, __ login, __ 2FA, __ email-change entries remaining",
                        );
                    },
                }
            }
        }
    }
}

[sww1235]

Just ran into this as well, while attempting to work around issues related to #3863.

[matthewhughes934]

@rustbot claim