error: ~const can only be applied to `#[const_trait]` traits
  --> $DIR/const-closures.rs:8:19
   |
LL |         F: ~const FnOnce() -> u8,
   |                   ^^^^^^^^^^^^^^

error: ~const can only be applied to `#[const_trait]` traits
  --> $DIR/const-closures.rs:9:19
   |
LL |         F: ~const FnMut() -> u8,
   |                   ^^^^^^^^^^^^^

error: ~const can only be applied to `#[const_trait]` traits
  --> $DIR/const-closures.rs:10:19
   |
LL |         F: ~const Fn() -> u8,
   |                   ^^^^^^^^^^

error: ~const can only be applied to `#[const_trait]` traits
  --> $DIR/const-closures.rs:23:27
   |
LL | const fn answer<F: ~const Fn() -> u8>(f: &F) -> u8 {
   |                           ^^^^^^^^^^

error: aborting due to 4 previous errors