error[E0229]: associated item constraints are not allowed here
  --> $DIR/issue-43431.rs:9:27
   |
LL |         <Self as Fn(A) -> B>::call(self, (a,))
   |                           ^ associated item constraint not allowed here

error: aborting due to 1 previous error

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