error: unconstrained opaque type
  --> $DIR/drop-analysis-on-unconstrained-tait.rs:5:24
   |
LL | pub type OpaqueBlock = impl Trait;
   |                        ^^^^^^^^^^
   |
   = note: `OpaqueBlock` must be used in combination with a concrete type within the same crate

error: aborting due to 1 previous error