Double dereference operator on self in Deref trait implementation for Box [duplicate]

Question

Looking at implementation of Deref trait for Box:

impl<T: ?Sized, A: Allocator> const Deref for Box<T, A> {
    type Target = T;

    fn deref(&self) -> &T {
        &**self
    }
}

i cannot understand double use of dereference operator * on self. By implementing Deref trait that way on a custom type, obviously the compiler complains about a recursive call. I'm missing something...