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use std::ops::{Deref, DerefMut}; pub struct Guard<T, F> where F: FnMut(&mut T) { __dropfn: F, __value: T, } pub fn guard<T, F>(v: T, dropfn: F) -> Guard<T, F> where F: FnMut(&mut T) { Guard{__value: v, __dropfn: dropfn} } impl<T, F> Deref for Guard<T, F> where F: FnMut(&mut T) { type Target = T; fn deref(&self) -> &T { &self.__value } } impl<T, F> DerefMut for Guard<T, F> where F: FnMut(&mut T) { fn deref_mut(&mut self) -> &mut T { &mut self.__value } } impl<T, F> Drop for Guard<T, F> where F: FnMut(&mut T) { fn drop(&mut self) { (self.__dropfn)(&mut self.__value) } }