Error code E0583
A file wasn't found for an out-of-line module.
Erroneous code example:
mod file_that_doesnt_exist; // error: file not found for module fn main() {}
Please be sure that a file corresponding to the module exists. If you
want to use a module named file_that_doesnt_exist, you need to have a file
named file_that_doesnt_exist.rs or file_that_doesnt_exist/mod.rs in the
same directory.