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>); | ------------------------ this field does not implement `Copy` ... LL | impl<'tcx, T> Copy for List<'tcx, T> {} | ^^^^^^^^^^^^^ | note: the `Copy` impl for `Interned<'tcx, ListS>` requires that `OpaqueListContents: Sized` --> $DIR/deep-bad-copy-reason.rs:23:26 | LL | pub struct List<'tcx, T>(Interned<'tcx, ListS>); | ^^^^^^^^^^^^^^^^^^^^^^^^ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0204`.