error[E0204]: the trait `Copy` cannot be implemented for this type
  --> $DIR/deep-bad-copy-reason.rs:33:24
   |
LL | pub struct List<'tcx, T>(Interned<'tcx, ListS<T>>);
   |                          ------------------------ this field does not implement `Copy`
...
LL | impl<'tcx, T> Copy for List<'tcx, T> {}
   |                        ^^^^^^^^^^^^^
   |
note: the `Copy` impl for `Interned<'tcx, ListS<T>>` requires that `OpaqueListContents: Sized`
  --> $DIR/deep-bad-copy-reason.rs:23:26
   |
LL | pub struct List<'tcx, T>(Interned<'tcx, ListS<T>>);
   |                          ^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0204`.