1error[E0631]: type mismatch in function arguments 2 --> $DIR/fn-variance-1.rs:11:15 3 | 4LL | fn takes_mut(x: &mut isize) { } 5 | --------------------------- found signature of `for<'r> fn(&'r mut isize) -> _` 6... 7LL | apply(&3, takes_mut); 8 | ----- ^^^^^^^^^ expected signature of `fn(&{integer}) -> _` 9 | | 10 | required by a bound introduced by this call 11 | 12note: required by a bound in `apply` 13 --> $DIR/fn-variance-1.rs:5:37 14 | 15LL | fn apply<T, F>(t: T, f: F) where F: FnOnce(T) { 16 | ^^^^^^^^^ required by this bound in `apply` 17 18error[E0631]: type mismatch in function arguments 19 --> $DIR/fn-variance-1.rs:15:19 20 | 21LL | fn takes_imm(x: &isize) { } 22 | ----------------------- found signature of `for<'r> fn(&'r isize) -> _` 23... 24LL | apply(&mut 3, takes_imm); 25 | ----- ^^^^^^^^^ expected signature of `fn(&mut {integer}) -> _` 26 | | 27 | required by a bound introduced by this call 28 | 29note: required by a bound in `apply` 30 --> $DIR/fn-variance-1.rs:5:37 31 | 32LL | fn apply<T, F>(t: T, f: F) where F: FnOnce(T) { 33 | ^^^^^^^^^ required by this bound in `apply` 34 35error: aborting due to 2 previous errors 36 37For more information about this error, try `rustc --explain E0631`. 38