pub trait CloneToAny {
/// Clone `self` into a new `Box<dyn CloneAny>` object.
fn clone_to_any(&self) -> Box<dyn CloneAny>;
-
- /// Clone `self` into a new `Box<dyn CloneAny + Send>` object.
- fn clone_to_any_send(&self) -> Box<dyn CloneAny + Send> where Self: Send;
-
- /// Clone `self` into a new `Box<dyn CloneAny + Sync>` object.
- fn clone_to_any_sync(&self) -> Box<dyn CloneAny + Sync> where Self: Sync;
-
- /// Clone `self` into a new `Box<dyn CloneAny + Send + Sync>` object.
- fn clone_to_any_send_sync(&self) -> Box<dyn CloneAny + Send + Sync> where Self: Send + Sync;
}
impl<T: Any + Clone> CloneToAny for T {
fn clone_to_any(&self) -> Box<dyn CloneAny> {
Box::new(self.clone())
}
-
- #[inline]
- fn clone_to_any_send(&self) -> Box<dyn CloneAny + Send> where Self: Send {
- Box::new(self.clone())
- }
-
- #[inline]
- fn clone_to_any_sync(&self) -> Box<dyn CloneAny + Sync> where Self: Sync {
- Box::new(self.clone())
- }
-
- #[inline]
- fn clone_to_any_send_sync(&self) -> Box<dyn CloneAny + Send + Sync> where Self: Send + Sync {
- Box::new(self.clone())
- }
-}
-
-macro_rules! define {
- (CloneAny) => {
- /// A type to emulate dynamic typing.
- ///
- /// Every type with no non-`'static` references implements `Any`.
- define!(CloneAny remainder);
- };
- (Any) => {
- /// A type to emulate dynamic typing with cloning.
- ///
- /// Every type with no non-`'static` references that implements `Clone` implements `Any`.
- define!(Any remainder);
- };
- ($t:ident remainder) => {
- /// See the [`std::any` documentation](https://doc.rust-lang.org/std/any/index.html) for
- /// more details on `Any` in general.
- ///
- /// This trait is not `std::any::Any` but rather a type extending that for this library’s
- /// purposes so that it can be combined with marker traits like
- /// <code><a class=trait title=core::marker::Send
- /// href=http://doc.rust-lang.org/std/marker/trait.Send.html>Send</a></code> and
- /// <code><a class=trait title=core::marker::Sync
- /// href=http://doc.rust-lang.org/std/marker/trait.Sync.html>Sync</a></code>.
- ///
- define!($t trait);
- };
- (CloneAny trait) => {
- /// See also [`Any`](trait.Any.html) for a version without the `Clone` requirement.
- pub trait CloneAny: Any + CloneToAny { }
- impl<T: StdAny + Clone> CloneAny for T { }
- };
- (Any trait) => {
- /// See also [`CloneAny`](trait.CloneAny.html) for a cloneable version of this trait.
- pub trait Any: StdAny { }
- impl<T: StdAny> Any for T { }
- };
}
macro_rules! impl_clone {
- ($t:ty, $method:ident) => {
+ ($t:ty) => {
impl Clone for Box<$t> {
#[inline]
fn clone(&self) -> Box<$t> {
- (**self).$method()
+ // SAFETY: this dance is to reapply any Send/Sync marker. I’m not happy about this
+ // approach, given that I used to do it in safe code, but then came a dodgy
+ // future-compatibility warning where_clauses_object_safety, which is spurious for
+ // auto traits but still super annoying (future-compatibility lints seem to mean
+ // your bin crate needs a corresponding allow!). Although I explained my plight¹
+ // and it was all explained and agreed upon, no action has been taken. So I finally
+ // caved and worked around it by doing it this way, which matches what’s done for
+ // std::any², so it’s probably not *too* bad.
+ //
+ // ¹ https://github.com/rust-lang/rust/issues/51443#issuecomment-421988013
+ // ² https://github.com/rust-lang/rust/blob/e7825f2b690c9a0d21b6f6d84c404bb53b151b38/library/alloc/src/boxed.rs#L1613-L1616
+ let clone: Box<dyn CloneAny> = (**self).clone_to_any();
+ let raw: *mut dyn CloneAny = Box::into_raw(clone);
+ unsafe { Box::from_raw(raw as *mut $t) }
}
}
}
}
}
-define!(Any);
+/// A type to emulate dynamic typing.
+///
+/// Every type with no non-`'static` references implements `Any`.
+/// See the [`std::any` documentation](https://doc.rust-lang.org/std/any/index.html) for
+/// more details on `Any` in general.
+///
+/// This trait is not `std::any::Any` but rather a type extending that for this library’s
+/// purposes so that it can be combined with marker traits like
+/// <code><a class=trait title=core::marker::Send
+/// href=http://doc.rust-lang.org/std/marker/trait.Send.html>Send</a></code> and
+/// <code><a class=trait title=core::marker::Sync
+/// href=http://doc.rust-lang.org/std/marker/trait.Sync.html>Sync</a></code>.
+///
+/// See also [`CloneAny`](trait.CloneAny.html) for a cloneable version of this trait.
+pub trait Any: StdAny { }
+impl<T: StdAny> Any for T { }
implement!(Any,);
implement!(Any, + Send);
implement!(Any, + Sync);
implement!(Any, + Send + Sync);
+
+/// A type to emulate dynamic typing with cloning.
+///
+/// Every type with no non-`'static` references that implements `Clone` implements `Any`.
+/// See the [`std::any` documentation](https://doc.rust-lang.org/std/any/index.html) for
+/// more details on `Any` in general.
+///
+/// This trait is not `std::any::Any` but rather a type extending that for this library’s
+/// purposes so that it can be combined with marker traits like
+/// <code><a class=trait title=core::marker::Send
+/// href=http://doc.rust-lang.org/std/marker/trait.Send.html>Send</a></code> and
+/// <code><a class=trait title=core::marker::Sync
+/// href=http://doc.rust-lang.org/std/marker/trait.Sync.html>Sync</a></code>.
+///
+/// See also [`Any`](trait.Any.html) for a version without the `Clone` requirement.
+pub trait CloneAny: Any + CloneToAny { }
+impl<T: StdAny + Clone> CloneAny for T { }
implement!(CloneAny,);
implement!(CloneAny, + Send);
implement!(CloneAny, + Sync);
implement!(CloneAny, + Send + Sync);
-
-define!(CloneAny);
-impl_clone!(dyn CloneAny, clone_to_any);
-impl_clone!(dyn CloneAny + Send, clone_to_any_send);
-impl_clone!(dyn CloneAny + Sync, clone_to_any_sync);
-impl_clone!(dyn CloneAny + Send + Sync, clone_to_any_send_sync);
+impl_clone!(dyn CloneAny);
+impl_clone!(dyn CloneAny + Send);
+impl_clone!(dyn CloneAny + Sync);
+impl_clone!(dyn CloneAny + Send + Sync);