fmt does not find modules inside inline modules inside non-inline modules

[heftig]

Problem
cargo fmt does not processes modules that are referenced in an inline mod in a non-inline mod.

This is slightly more complex case than #4874, so it seems that bug was not fully fixed.

Steps

crate tree:

.
├── Cargo.toml
└── src
    ├── foo
    │   └── bar
    │       └── baz.rs
    ├── foo.rs
    └── main.rs

src/main.rs:

fn main() {
    println!("Hello, world!");
}

mod foo;

src/foo.rs:

mod bar {
    mod baz;
}

src/foo/bar/baz.rs: empty

1.52.0 is fine:

> cargo +1.52.0 fmt -- -v
Formatting /home/jan/x/src/foo/bar/baz.rs
Formatting /home/jan/x/src/foo.rs
Formatting /home/jan/x/src/main.rs

1.53.0, stable and nightly are broken:

> cargo +1.53.0 fmt -- -v
Formatting /home/jan/x/src/foo.rs
Formatting /home/jan/x/src/main.rs

> cargo +stable fmt -- -v
Formatting /home/jan/x/src/foo.rs
Formatting /home/jan/x/src/main.rs

> cargo +nightly fmt -- -v
Formatting /home/jan/x/src/foo.rs
Formatting /home/jan/x/src/main.rs

Notes

Output of rustfmt --version:

• 1.52.0: rustfmt 1.4.36-stable (7de6968 2021-02-07)
• 1.53.0: rustfmt 1.4.37-stable (2a3635d 2021-05-04)
• stable: rustfmt 1.4.37-stable (59eed8a 2021-11-01)
• nightly: rustfmt 1.4.38-nightly (baba668 2021-11-03)

Rust via rustup 1.24.3, Arch Linux.

[calebcartwright]

Thanks for the report @heftig and the repro case! Believe I know what the issue is so I'll take a look later today after work.

I still suspect we could handle our mod/file resolution process a bit more simply, but can never seem to find the time for investigating a more holistic refactor. Will make sure the fix for this gets pulled into the next sync though