The borrowing the closure does doesn't change the type of the captured variable. count is of type i32 inside and outside the closure; the &mut i32 is only part of how the compiler implements access to count inside the closure.
The borrowing the closure does doesn't change the type of the captured variable. count is of type i32 inside and outside the closure; the &mut i32 is only part of how the compiler implements access to count inside the closure.