`#[cfg_attr(..., path = ...)]` on inline modules is not recognized

[purplesyringa]

// lib.rs
#[cfg_attr(unix, path = "meow_unix")]
#[cfg_attr(not(unix), path = "meow_not_unix")]
mod meow {
    mod mrrp;
}

// meow_unix/mrrp.rs
broken

// meow_not_unix/mrrp.rs
broken

$ cargo fmt
Error writing files: failed to resolve mod `mrrp`: /home/purplesyringa/rust-test/src/meow/mrrp.rs does not exist

Creating meow/mrrp.rs removes the error message, but doesn't format the (broken) included files.

This is a variant of #2407, which was fixed by #3604, but apparently not for path attributes on inline mod blocks. The correct path resolution here is to have meow::mrrp refer either to meow_unix/mrrp.rs or meow_not_unix/mrrp.rs, and indeed rustc sees it this way (reference), but rustfmt doesn't. This specifically affects path behind cfg_attr; normal path works correctly.

Meta

rustfmt --version:

rustfmt 1.10.0-nightly (f7d782a3be 2026-08-19)

@rustbot label +A-cfg +A-modules

[ytmimi]

Thanks for linking to the reference. I honestly didn't know that you could add a #[path] attribute to inline modules.

[ytmimi]

This case from the reference is also one that I'm not sure we have working:

#[path = "thread_files"]
mod thread {
    // Load the `local_data` module from `thread_files/tls.rs` relative to
    // this source file's directory.
    #[path = "tls.rs"]
    mod local_data;
}