error[E0308]: mismatched types
  --> $DIR/issue-101280.rs:6:5
   |
LL | fn f<'r>(f: fn(Cell<(&'r i32, &i32)>)) -> Ty {
   |                                           -- expected `for<'r> fn(Cell<(&'r i32, &'r i32)>)` because of return type
LL |     f
   |     ^ one type is more general than the other
   |
   = note: expected fn pointer `for<'r> fn(Cell<(&'r i32, &'r i32)>)`
              found fn pointer `for<'a> fn(Cell<(&'r i32, &'a i32)>)`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.