1error[E0631]: type mismatch in closure arguments 2 --> $DIR/unboxed-closures-vtable-mismatch.rs:16:24 3 | 4LL | let f = to_fn_mut(|x: usize, y: isize| -> isize { (x as isize) + y }); 5 | ----------------------------- found signature of `fn(usize, isize) -> _` 6LL | 7LL | let z = call_it(3, f); 8 | ------- ^ expected signature of `fn(isize, isize) -> _` 9 | | 10 | required by a bound introduced by this call 11 | 12note: required by a bound in `call_it` 13 --> $DIR/unboxed-closures-vtable-mismatch.rs:7:14 14 | 15LL | fn call_it<F:FnMut(isize,isize)->isize>(y: isize, mut f: F) -> isize { 16 | ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `call_it` 17 18error: aborting due to previous error 19 20For more information about this error, try `rustc --explain E0631`. 21