error[E0782]: expected a type, found a trait
  --> $DIR/avoid-ice-on-warning-2.rs:4:13
   |
LL | fn id<F>(f: Copy) -> usize {
   |             ^^^^
   |
   = note: `Copy` it is dyn-incompatible, so it can't be `dyn`
help: use a new generic type parameter, constrained by `Copy`
   |
LL | fn id<F, T: Copy>(f: T) -> usize {
   |        +++++++++     ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
   |
LL | fn id<F>(f: impl Copy) -> usize {
   |             ++++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0782`.