error[E0391]: cycle detected when computing the super predicates of `T1`
  --> $DIR/issue-12511.rs:1:1
   |
LL | trait T1 : T2 {
   | ^^^^^^^^^^^^^
   |
note: ...which requires computing the super traits of `T1`...
  --> $DIR/issue-12511.rs:1:12
   |
LL | trait T1 : T2 {
   |            ^^
note: ...which requires computing the super predicates of `T2`...
  --> $DIR/issue-12511.rs:5:1
   |
LL | trait T2 : T1 {
   | ^^^^^^^^^^^^^
note: ...which requires computing the super traits of `T2`...
  --> $DIR/issue-12511.rs:5:12
   |
LL | trait T2 : T1 {
   |            ^^
   = note: ...which again requires computing the super predicates of `T1`, completing the cycle
note: cycle used when collecting item types in top-level module
  --> $DIR/issue-12511.rs:1:1
   |
LL | / trait T1 : T2 {
LL | |
LL | | }
   | |_^

error: aborting due to previous error

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