Function idata::steal_borrow

pub fn steal_borrow<T>(target: &mut T, f: &dyn Fn(T) -> T)

&mut propagates mutability to top This is bad

You could have also a type working by owner shipt (to avoid mutability propagation)

In several cases you will have problems due to references

To avoid it, steal_borrow will let you execute as owner a function

   extern crate idata;

   struct Ex {
       val1: u16,
       val2: u32,
   }

   impl Ex {
       fn inc(mut self) -> Self {
           self.val1 += 1;
           self.val2 += 2;
           self
       }
   }

   fn test(rm_ex: &mut Ex) {
       idata::steal_borrow(rm_ex, &|o : Ex| o.inc() );
   }

   fn main() {
       let mut ex = Ex{ val1: 0, val2: 0};
       test(&mut ex);

       assert!(ex.val1 == 1);
       assert!(ex.val2 == 2);
   }