error: diagnostic slug and crate name do not match
  --> $DIR/enforce_slug_naming.rs:23:8
   |
LL | #[diag(compiletest_example, code = "E0123")]
   |        ^^^^^^^^^^^^^^^^^^^
   |
   = note: slug is `compiletest_example` but the crate name is `rustc_dummy`
   = help: expected a slug starting with `dummy_...`

error: aborting due to 1 previous error