Error writing files: io error: Failed to find module

[dtolnay]

I have two source files:

src/lib.rs

#[path = "."]
pub mod a {
    pub mod b;
}

src/b.rs

// (empty file)

cargo check seems to be fine with this layout, and the code compiles. But cargo fmt fails with:

Error writing files: io error: Failed to find module b in "." None

[josephlr]

I've also hit this issue. It seems like rustfmt does not like path-renamed modules.

[nocker01]

Hi, I think I'm still experiencing this issue. I'm new to Rust...

I am using relative paths to access different modules. My project compiles fine but "cargo fmt" does not work for me. I'm using Windows 7 and have switched to a nightly build of rustup:
rustup 1.22.1 (b01adbbc3 2020-07-08)
nightly-i686-pc-windows-gnu

Previously when I ran the command "cargo fmt" I would get the error that is the subject of this thread. I now when I run it I get the following error:
error: couldn't read \?\C:\projects\application\main..\common\debug.rs: The filename, directory name, or volume label syntax is incorrect. (os error 123)
Error writing files: failed to resolve mod debug: \?\C:\projects\application\main..\common\debug.rs does not exist

This does tell me more clearly the path that could not be found but the file is definately in the directory:
C:\projects\application\common\debug.rs

EDIT: I should say my directory structure is:
C:\projects\application\common\debug.rs
C:\projects\application\main\main.rs