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 predicates of `T`
  --> $DIR/issue-20772.rs:1:1
   |
LL | trait T : Iterator<Item=Self::Item>
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

error: aborting due to 1 previous error

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