error: malformed `rustc_lint_diagnostics` attribute input
  --> $DIR/diagnostics_incorrect.rs:10:5
   |
LL |     #[rustc_lint_diagnostics(a)]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[rustc_lint_diagnostics]`

error: attribute should be applied to a function definition
  --> $DIR/diagnostics_incorrect.rs:5:1
   |
LL | #[rustc_lint_diagnostics]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^
LL |
LL | struct Foo;
   | ----------- not a function definition

error: aborting due to 2 previous errors