warning: deny(warnings) incompatible with previous forbid
  --> $DIR/issue-80988.rs:7:8
   |
LL | #![forbid(warnings)]
   |           -------- `forbid` level set here
LL |
LL | #[deny(warnings)]
   |        ^^^^^^^^ overruled by previous forbid
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #81670 <https://github.com/rust-lang/rust/issues/81670>
   = note: `#[warn(forbidden_lint_groups)]` on by default

warning: 1 warning emitted