error: `#[cfg_attr]` does not expand to any attributes
  --> $DIR/cfg-attr-empty-is-unused.rs:7:1
   |
LL | #[cfg_attr(FALSE,)]
   | ^^^^^^^^^^^^^^^^^^^
   |
note: the lint level is defined here
  --> $DIR/cfg-attr-empty-is-unused.rs:5:9
   |
LL | #![deny(unused)]
   |         ^^^^^^
   = note: `#[deny(unused_attributes)]` implied by `#[deny(unused)]`

error: `#[cfg_attr]` does not expand to any attributes
  --> $DIR/cfg-attr-empty-is-unused.rs:10:1
   |
LL | #[cfg_attr(TRUE,)]
   | ^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors