error: concrete type differs from previous defining opaque type use
  --> $DIR/recursive-tait-conflicting-defn-2.rs:12:5
   |
LL |     transform::<Op>()
   |     ^^^^^^^^^^^^^^^^^ expected `&'static &'static str`, got `impl std::fmt::Display`
   |
note: previous use here
  --> $DIR/recursive-tait-conflicting-defn-2.rs:6:18
   |
LL | fn foo() -> Op { &"hello world" }
   |                  ^^^^^^^^^^^^^^

error: aborting due to previous error