error[E0229]: associated type bindings are not allowed here
  --> $DIR/issue-39259.rs:6:17
   |
LL | impl Fn(u32) -> u32 for S {
   |                 ^^^ associated type not allowed here
   |
help: parenthesized trait syntax expands to `Fn<(u32,), Output=u32>`
  --> $DIR/issue-39259.rs:6:6
   |
LL | impl Fn(u32) -> u32 for S {
   |      ^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0229`.