Mutable variable swap in rust

option_map_mut.rs

// This allows you to consume a variable ane replace it with a new value

fn option_map_mut<T, F: FnOnce(T) -> T>(x: &mut Option<T>, f: F) {             
   match *x {   
      Some(_) => {     
         *x = Some(f(x.take().unwrap()));
      }
      None => {}     
   }
}