error[E0277]: the trait bound `T: Pointee` is not satisfied in `PtrComponents<T>`
  --> $DIR/issue-81199.rs:5:17
   |
LL |     components: PtrComponents<T>,
   |                 ^^^^^^^^^^^^^^^^ within `PtrComponents<T>`, the trait `Pointee` is not implemented for `T`
   |
note: required because it appears within the type `PtrComponents<T>`
  --> $DIR/issue-81199.rs:10:8
   |
LL | struct PtrComponents<T: Pointee + ?Sized> {
   |        ^^^^^^^^^^^^^
   = note: no field of a union may have a dynamically sized type
   = help: change the field's type to have a statically known size
help: consider further restricting this bound
   |
LL | union PtrRepr<T: ?Sized + Pointee> {
   |                         +++++++++
help: borrowed types always have a statically known size
   |
LL |     components: &PtrComponents<T>,
   |                 +
help: the `Box` type always has a statically known size and allocates its contents in the heap
   |
LL |     components: Box<PtrComponents<T>>,
   |                 ++++                +

error: aborting due to previous error

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