src/test/run-pass/arbitrary_self_types_pointers_and_wrappers.rs

// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![feature(arbitrary_self_types, unsize, coerce_unsized, dispatch_from_dyn)]
#![feature(rustc_attrs)]

use std::{
    ops::{Deref, CoerceUnsized, DispatchFromDyn},
    marker::Unsize,
};

struct Ptr<T: ?Sized>(Box<T>);

impl<T: ?Sized> Deref for Ptr<T> {
    type Target = T;

    fn deref(&self) -> &T {
        &*self.0
    }
}

impl<T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<Ptr<U>> for Ptr<T> {}
impl<T: Unsize<U> + ?Sized, U: ?Sized> DispatchFromDyn<Ptr<U>> for Ptr<T> {}

struct Wrapper<T: ?Sized>(T);

impl<T: ?Sized> Deref for Wrapper<T> {
    type Target = T;

    fn deref(&self) -> &T {
        &self.0
    }
}

impl<T: CoerceUnsized<U>, U> CoerceUnsized<Wrapper<U>> for Wrapper<T> {}
impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<Wrapper<U>> for Wrapper<T> {}


trait Trait {
    // This method isn't object-safe yet. Unsized by-value `self` is object-safe (but not callable
    // without unsized_locals), but wrappers arond `Self` currently are not.
    // FIXME (mikeyhew) uncomment this when unsized rvalues object-safety is implemented
    // fn wrapper(self: Wrapper<Self>) -> i32;
    fn ptr_wrapper(self: Ptr<Wrapper<Self>>) -> i32;
    fn wrapper_ptr(self: Wrapper<Ptr<Self>>) -> i32;
    fn wrapper_ptr_wrapper(self: Wrapper<Ptr<Wrapper<Self>>>) -> i32;
}

impl Trait for i32 {
    fn ptr_wrapper(self: Ptr<Wrapper<Self>>) -> i32 {
        **self
    }
    fn wrapper_ptr(self: Wrapper<Ptr<Self>>) -> i32 {
        **self
    }
    fn wrapper_ptr_wrapper(self: Wrapper<Ptr<Wrapper<Self>>>) -> i32 {
        ***self
    }
}

fn main() {
    let pw = Ptr(Box::new(Wrapper(5))) as Ptr<Wrapper<dyn Trait>>;
    assert_eq!(pw.ptr_wrapper(), 5);

    let wp = Wrapper(Ptr(Box::new(6))) as Wrapper<Ptr<dyn Trait>>;
    assert_eq!(wp.wrapper_ptr(), 6);

    let wpw = Wrapper(Ptr(Box::new(Wrapper(7)))) as Wrapper<Ptr<Wrapper<dyn Trait>>>;
    assert_eq!(wpw.wrapper_ptr_wrapper(), 7);
}