error[E0277]: `&T` needs to have the same ABI as a pointer
  --> $DIR/check-size-at-cast-polymorphic-bad.rs:15:15
   |
LL | fn polymorphic<T: Debug + ?Sized>(t: &T) {
   |                - this type parameter needs to be `Sized`
LL |     dyn_debug(t);
   |               ^ `&T` needs to be a pointer-like type
   |
   = note: required for `&T` to implement `PointerLike`
help: consider removing the `?Sized` bound to make the type parameter `Sized`
   |
LL - fn polymorphic<T: Debug + ?Sized>(t: &T) {
LL + fn polymorphic<T: Debug>(t: &T) {
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.