error: cannot implement trait on type alias impl trait
  --> $DIR/issue-65384.rs:11:1
   |
LL | impl MyTrait for Bar {}
   | ^^^^^^^^^^^^^^^^^^^^
   |
note: type alias impl trait defined here
  --> $DIR/issue-65384.rs:9:12
   |
LL | type Bar = impl MyTrait;
   |            ^^^^^^^^^^^^

error: aborting due to previous error