error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
  --> $DIR/ice-6251.rs:4:45
   |
LL | fn bug<T>() -> impl Iterator<Item = [(); { |x: [u8]| x }]> {
   |                                             ^ doesn't have a size known at compile-time
   |
   = help: the trait `std::marker::Sized` is not implemented for `[u8]`
   = help: unsized fn params are gated as an unstable feature
help: function arguments must have a statically known size, borrowed slices always have a known size
   |
LL | fn bug<T>() -> impl Iterator<Item = [(); { |x: &[u8]| x }]> {
   |                                                +

error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
  --> $DIR/ice-6251.rs:4:54
   |
LL | fn bug<T>() -> impl Iterator<Item = [(); { |x: [u8]| x }]> {
   |                                                      ^ doesn't have a size known at compile-time
   |
   = help: the trait `std::marker::Sized` is not implemented for `[u8]`
   = note: the return type of a function must have a statically known size

error[E0308]: mismatched types
  --> $DIR/ice-6251.rs:4:44
   |
LL | fn bug<T>() -> impl Iterator<Item = [(); { |x: [u8]| x }]> {
   |                                            ^^^^^^^^^^^ expected `usize`, found closure
   |
   = note: expected type `usize`
           found closure `{closure@$DIR/ice-6251.rs:4:44: 4:53}`

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.