Compiling hello v0.1.0 (file:///home/rust/hello) error[E0658]: mod statements in non-mod.rs files are unstable (see issue #44660) --> src/sound.rs:1:9 | 1 | pub mod instrument; | ^^^^^^^^^^ | = help: on stable builds, rename this file to sound/mod.rs error: aborting due to previous error For more information about this error, try `rustc --explain E0658`. error: Could not compile `hello`.
To learn more, run the command again with --verbose.
I am writing the code according to Separating Modules into Different Files in the official tutorial of the rust compiler language. Why is it wrong?