error[E0658]: non-inline modules in proc macro input are unstable
 --> tests/ui/mod-must-be-inline.rs:4:1
  |
4 | mod tests;
  | ^^^^^^^^^^
  |
  = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information

error: module must be inline (e.g. `mod foo {}`)
 --> tests/ui/mod-must-be-inline.rs:4:1
  |
4 | mod tests;
  | ^^^