//! cloneable `Any` and with the `Send` and `Sync` bounds possible on both `Any` and `CloneAny`.
use std::fmt;
-use std::any::Any as StdAny;
+use std::any::Any;
#[doc(hidden)]
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! 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) }
+ }
+ }
+
+ impl fmt::Debug for $t {
+ #[inline]
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.pad(stringify!($t))
}
}
}
macro_rules! implement {
($base:ident, $(+ $bounds:ident)*) => {
- impl fmt::Debug for dyn $base $(+ $bounds)* {
- #[inline]
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- f.pad(stringify!(dyn $base $(+ $bounds)*))
- }
- }
-
impl UncheckedAnyExt for dyn $base $(+ $bounds)* {
#[inline]
unsafe fn downcast_ref_unchecked<T: 'static>(&self) -> &T {
}
}
-/// 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>.
+/// [`Any`], but with cloning.
///
-/// See also [`Any`](trait.Any.html) for a version without the `Clone` requirement.
+/// Every type with no non-`'static` references that implements `Clone` implements `CloneAny`.
+/// See [`std::any`] for more details on `Any` in general.
pub trait CloneAny: Any + CloneToAny { }
-impl<T: StdAny + Clone> CloneAny for T { }
+impl<T: Any + Clone> CloneAny for T { }
implement!(CloneAny,);
implement!(CloneAny, + Send);
-implement!(CloneAny, + Sync);
implement!(CloneAny, + Send + Sync);
-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 + Send + Sync);