error[E0271]: type mismatch resolving `<() as Array<'a>>::Element == ()`
  --> $DIR/issue-39970.rs:19:5
   |
LL |     <() as Visit>::visit();
   |     ^^^^^^^^^^^^^^^^^^^^ type mismatch resolving `<() as Array<'a>>::Element == ()`
   |
note: expected this to be `()`
  --> $DIR/issue-39970.rs:10:20
   |
LL |     type Element = &'a ();
   |                    ^^^^^^
note: required for `()` to implement `Visit`
  --> $DIR/issue-39970.rs:13:6
   |
LL | impl Visit for () where
   |      ^^^^^     ^^
LL |     //(): for<'a> Array<'a, Element=&'a ()>, // No ICE
LL |     (): for<'a> Array<'a, Element=()>, // ICE
   |                           ---------- unsatisfied trait bound introduced here

error: aborting due to previous error

For more information about this error, try `rustc --explain E0271`.