error[E0277]: the trait bound `(): T` is not satisfied
  --> $DIR/impl_trait_fallback2.rs:8:25
   |
LL | fn should_ret_unit() -> impl T {
   |                         ^^^^^^ the trait `T` is not implemented for `()`
   |
   = help: the trait `T` is implemented for `i32`

error[E0277]: the trait bound `(): T` is not satisfied
  --> $DIR/impl_trait_fallback2.rs:15:11
   |
LL | fn a() -> Foo {
   |           ^^^ the trait `T` is not implemented for `()`
   |
   = help: the trait `T` is implemented for `i32`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.