error: concrete type differs from previous defining opaque type use
  --> $DIR/generic_different_defining_uses.rs:11:1
   |
LL | / fn my_iter2<T>(t: T) -> MyIter<T> {
LL | |     Some(t).into_iter()
LL | | }
   | |_^ expected `std::iter::Once<T>`, got `std::option::IntoIter<T>`
   |
note: previous use here
  --> $DIR/generic_different_defining_uses.rs:7:1
   |
LL | / fn my_iter<T>(t: T) -> MyIter<T> {
LL | |     std::iter::once(t)
LL | | }
   | |_^

error: aborting due to previous error