Rust error E0761: multiple candidate files were found for an out-of-line module

The compiler team's explanation

Multiple candidate files were found for an out-of-line module.

Erroneous code example:

// file: ambiguous_module/mod.rs

fn foo() {}

// file: ambiguous_module.rs

fn foo() {}

// file: lib.rs

mod ambiguous_module; // error: file for module `ambiguous_module`
                      // found at both ambiguous_module.rs and
                      // ambiguous_module/mod.rs

Please remove this ambiguity by deleting/renaming one of the candidate files.

From rustc --explain E0761 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.