Code shared from the Rust Playground

playground.rs

#![feature(pin)]

use std::marker::Unpin;
use std::ops::{Deref, DerefMut};
use std::rc::Rc;
use std::sync::Arc;

#[derive(Copy, Clone)]
pub struct Pin<P> {
    pointer: P,
}

impl<P, T> Deref for Pin<P> where
    P: Deref<Target = T>,
{
    type Target = T;
    fn deref(&self) -> &T {
        &*self.pointer
    }
}

impl<P, T> DerefMut for Pin<P> where
    P: DerefMut<Target = T>,
    T: Unpin,
{
    fn deref_mut(&mut self) -> &mut T {
        &mut *self.pointer
    }
}

impl<P> Pin<P> {
    pub unsafe fn new_unchecked(pointer: P) -> Pin<P> {
        Pin { pointer }
    }
}

impl<P, T> Pin<P> where
    P: Deref<Target = T>,
{
    pub fn as_ref(this: &Pin<P>) -> Pin<&T> {
        Pin { pointer: &*this.pointer }
    }
}

impl<P, T> Pin<P> where
    P: DerefMut<Target = T>,
{
    pub fn as_mut(this: &mut Pin<P>) -> Pin<&mut T> {
        Pin { pointer: &mut *this.pointer }
    }

    pub unsafe fn get_mut_unchecked(&mut self) -> &mut T {
        &mut *self.pointer
    }
}

impl<T> From<Box<T>> for Pin<Box<T>> {
    fn from(pointer: Box<T>) -> Pin<Box<T>> {
        unsafe { Pin::new_unchecked(pointer) }
    }
}

pub unsafe trait Own: Deref + Sized where Self::Target: Sized {
    fn own(data: Self::Target) -> Self;
    
    fn pinned(data: Self::Target) -> Pin<Self> {
        unsafe { Pin::new_unchecked(Self::own(data)) }
    }
}

unsafe impl<T> Own for Box<T> {
    fn own(data: T) -> Box<T> {
        Box::new(data)
    }
}

unsafe impl<T> Own for Rc<T> {
    fn own(data: T) -> Rc<T> {
        Rc::new(data)
    }
}

unsafe impl<T> Own for Arc<T> {
    fn own(data: T) -> Arc<T> {
        Arc::new(data)
    }
}

impl<T> From<Vec<T>> for Pin<Vec<T>> {
    fn from(pointer: Vec<T>) -> Pin<Vec<T>> {
        unsafe { Pin::new_unchecked(pointer) }
    }
}

impl<P, T> Pin<P>
where
    P: DerefMut<Target = [T]>,
{
    pub fn index_pin<'a, I>(&'a mut self, idx: I) -> Pin<&'a mut I::Output> 
    where 
        I: SliceIndex<[T]>,
        T: 'a
    {
        unsafe {Pin::new_unchecked(&mut self.pointer[idx]) }
    }
}