error: cannot implement trait on type alias impl trait
  --> $DIR/issue-65384.rs:10:18
   |
LL | impl MyTrait for Bar {}
   |                  ^^^
   |
note: type alias impl trait defined here
  --> $DIR/issue-65384.rs:8:12
   |
LL | type Bar = impl MyTrait;
   |            ^^^^^^^^^^^^

error: aborting due to previous error