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
|
//@ check-pass
#![feature(derive_coerce_pointee)]
#[derive(core::marker::CoercePointee)]
#[repr(transparent)]
pub struct Ptr<'a, #[pointee] T: OnDrop + ?Sized, X> {
data: &'a mut T,
x: core::marker::PhantomData<X>,
}
pub trait OnDrop {
fn on_drop(&mut self);
}
#[derive(core::marker::CoercePointee)]
#[repr(transparent)]
pub struct Ptr2<'a, #[pointee] T: ?Sized, X>
where
T: OnDrop,
{
data: &'a mut T,
x: core::marker::PhantomData<X>,
}
pub trait MyTrait<T: ?Sized> {}
#[derive(core::marker::CoercePointee)]
#[repr(transparent)]
pub struct Ptr3<'a, #[pointee] T: ?Sized, X>
where
T: MyTrait<T>,
{
data: &'a mut T,
x: core::marker::PhantomData<X>,
}
#[derive(core::marker::CoercePointee)]
#[repr(transparent)]
pub struct Ptr4<'a, #[pointee] T: MyTrait<T> + ?Sized, X> {
data: &'a mut T,
x: core::marker::PhantomData<X>,
}
#[derive(core::marker::CoercePointee)]
#[repr(transparent)]
pub struct Ptr5<'a, #[pointee] T: ?Sized, X>
where
Ptr5Companion<T>: MyTrait<T>,
Ptr5Companion2: MyTrait<T>,
{
data: &'a mut T,
x: core::marker::PhantomData<X>,
}
pub struct Ptr5Companion<T: ?Sized>(core::marker::PhantomData<T>);
pub struct Ptr5Companion2;
#[derive(core::marker::CoercePointee)]
#[repr(transparent)]
pub struct Ptr6<'a, #[pointee] T: ?Sized, X: MyTrait<T> = (), const PARAM: usize = 0> {
data: &'a mut T,
x: core::marker::PhantomData<X>,
}
// a reduced example from https://lore.kernel.org/all/20240402-linked-list-v1-1-b1c59ba7ae3b@google.com/
#[repr(transparent)]
#[derive(core::marker::CoercePointee)]
pub struct ListArc<#[pointee] T, const ID: u64 = 0>
where
T: ListArcSafe<ID> + ?Sized,
{
arc: *const T,
}
pub trait ListArcSafe<const ID: u64> {}
fn main() {}
|
