error[E0119]: conflicting implementations of trait `Trait<_>`
  --> $DIR/issue-45814.rs:10:1
   |
LL | default impl<T, U> Trait<T> for U {}
   | --------------------------------- first implementation here
LL |
LL | impl<T> Trait<<T as Iterator>::Item> for T {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0119`.