1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
// run-pass
#![feature(arbitrary_self_types, unsize, coerce_unsized, dispatch_from_dyn)]
#![feature(rustc_attrs)]
use std::{
cell::Cell,
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 CellPtr<'a, T: ?Sized>(Cell<&'a T>);
impl<'a, T: ?Sized> Deref for CellPtr<'a, T> {
type Target = T;
fn deref(&self) -> &T {
self.0.get()
}
}
impl<'a, T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<CellPtr<'a, U>> for CellPtr<'a, T> {}
impl<'a, T: Unsize<U> + ?Sized, U: ?Sized> DispatchFromDyn<CellPtr<'a, U>> for CellPtr<'a, 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;
fn cell(self: CellPtr<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 cell(self: CellPtr<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);
let c = CellPtr(Cell::new(&8)) as CellPtr<dyn Trait>;
assert_eq!(c.cell(), 8);
}
|
