453d7dd9fca5604f602a4426e147e32e0429b626
1 //! The different types of `Any` for use in a map.
3 //! This stuff is all based on `std::any`, but goes a little further, with `CloneAny` being a
4 //! cloneable `Any` and with the `Send` and `Sync` bounds possible on both `Any` and `CloneAny`.
10 pub trait CloneToAny
{
11 /// Clone `self` into a new `Box<dyn CloneAny>` object.
12 fn clone_to_any(&self) -> Box
<dyn CloneAny
>;
15 impl<T
: Any
+ Clone
> CloneToAny
for T
{
17 fn clone_to_any(&self) -> Box
<dyn CloneAny
> {
18 Box
::new(self.clone())
22 macro_rules
! impl_clone
{
24 impl Clone
for Box
<$t
> {
26 fn clone(&self) -> Box
<$t
> {
27 // SAFETY: this dance is to reapply any Send/Sync marker. I’m not happy about this
28 // approach, given that I used to do it in safe code, but then came a dodgy
29 // future-compatibility warning where_clauses_object_safety, which is spurious for
30 // auto traits but still super annoying (future-compatibility lints seem to mean
31 // your bin crate needs a corresponding allow!). Although I explained my plight¹
32 // and it was all explained and agreed upon, no action has been taken. So I finally
33 // caved and worked around it by doing it this way, which matches what’s done for
34 // std::any², so it’s probably not *too* bad.
36 // ¹ https://github.com/rust-lang/rust/issues/51443#issuecomment-421988013
37 // ² https://github.com/rust-lang/rust/blob/e7825f2b690c9a0d21b6f6d84c404bb53b151b38/library/alloc/src/boxed.rs#L1613-L1616
38 let clone
: Box
<dyn CloneAny
> = (**self).clone_to_any();
39 let raw
: *mut dyn CloneAny
= Box
::into_raw(clone
);
40 unsafe { Box
::from_raw(raw
as *mut $t
) }
44 impl fmt
::Debug
for $t
{
46 fn fmt(&self, f
: &mut fmt
::Formatter
) -> fmt
::Result
{
53 #[allow(missing_docs)] // Bogus warning (it’s not public outside the crate), ☹
54 pub trait UncheckedAnyExt
: Any
{
55 unsafe fn downcast_ref_unchecked
<T
: Any
>(&self) -> &T
;
56 unsafe fn downcast_mut_unchecked
<T
: Any
>(&mut self) -> &mut T
;
57 unsafe fn downcast_unchecked
<T
: Any
>(self: Box
<Self>) -> Box
<T
>;
61 /// A trait for the conversion of an object into a boxed trait object.
62 pub trait IntoBox
<A
: ?Sized
+ UncheckedAnyExt
>: Any
{
63 /// Convert self into the appropriate boxed form.
64 fn into_box(self) -> Box
<A
>;
67 macro_rules
! implement
{
68 ($base
:ident
, $
(+ $bounds
:ident
)*) => {
69 impl UncheckedAnyExt
for dyn $base $
(+ $bounds
)* {
71 unsafe fn downcast_ref_unchecked
<T
: '
static>(&self) -> &T
{
72 &*(self as *const Self as *const T
)
76 unsafe fn downcast_mut_unchecked
<T
: '
static>(&mut self) -> &mut T
{
77 &mut *(self as *mut Self as *mut T
)
81 unsafe fn downcast_unchecked
<T
: '
static>(self: Box
<Self>) -> Box
<T
> {
82 Box
::from_raw(Box
::into_raw(self) as *mut T
)
86 impl<T
: $base $
(+ $bounds
)*> IntoBox
<dyn $base $
(+ $bounds
)*> for T
{
88 fn into_box(self) -> Box
<dyn $base $
(+ $bounds
)*> {
96 implement!(Any
, + Send
);
97 implement!(Any
, + Send
+ Sync
);
99 /// [`Any`], but with cloning.
101 /// Every type with no non-`'static` references that implements `Clone` implements `CloneAny`.
102 /// See [`std::any`] for more details on `Any` in general.
103 pub trait CloneAny
: Any
+ CloneToAny
{ }
104 impl<T
: Any
+ Clone
> CloneAny
for T
{ }
105 implement!(CloneAny
,);
106 implement!(CloneAny
, + Send
);
107 implement!(CloneAny
, + Send
+ Sync
);
108 impl_clone!(dyn CloneAny
);
109 impl_clone!(dyn CloneAny
+ Send
);
110 impl_clone!(dyn CloneAny
+ Send
+ Sync
);