error[E0391]: cycle detected when computing the super traits of `T` with associated type name `Item`
  --> $DIR/issue-20772.rs:1:1
   |
LL | trait T : Iterator<Item=Self::Item>
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ...which immediately requires computing the super traits of `T` with associated type name `Item` again
note: cycle used when computing the super traits of `T`
  --> $DIR/issue-20772.rs:1:1
   |
LL | trait T : Iterator<Item=Self::Item>
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0391`.