| #![deny(unsafe_code,rustdoc::bare_urls)] |
| #![cfg_attr(not(feature = "std"), no_std)] |
| //! [](https://github.com/marcianx/downcast-rs/actions) |
| //! [](https://crates.io/crates/downcast-rs) |
| //! [](https://docs.rs/downcast-rs) |
| //! |
| //! Rust enums are great for types where all variations are known beforehand. But a |
| //! container of user-defined types requires an open-ended type like a **trait |
| //! object**. Some applications may want to cast these trait objects back to the |
| //! original concrete types to access additional functionality and performant |
| //! inlined implementations. |
| //! |
| //! `downcast-rs` adds this downcasting support to trait objects using only safe |
| //! Rust. It supports **type parameters**, **associated types**, and **constraints**. |
| //! |
| //! # Usage |
| //! |
| //! Add the following to your `Cargo.toml`: |
| //! |
| //! ```toml |
| //! [dependencies] |
| //! downcast-rs = "2.0.1" |
| //! ``` |
| //! |
| //! This crate is `no_std` compatible. To use it without `std`: |
| //! |
| //! ```toml |
| //! [dependencies] |
| //! downcast-rs = { version = "2.0.1", default-features = false } |
| //! ``` |
| //! |
| //! To make a trait downcastable, make it extend either `Downcast` or `DowncastSync` and invoke |
| //! `impl_downcast!` on it as in the examples below. |
| //! |
| //! Since 2.0.0, the minimum supported Rust version is 1.56. |
| //! |
| //! ```rust |
| //! # use downcast_rs::{Downcast, impl_downcast}; |
| //! # #[cfg(feature = "sync")] |
| //! # use downcast_rs::DowncastSync; |
| //! trait Trait: Downcast {} |
| //! impl_downcast!(Trait); |
| //! |
| //! // Also supports downcasting `Arc`-ed trait objects by extending `DowncastSync` |
| //! // and starting `impl_downcast!` with `sync`. |
| //! # #[cfg(feature = "sync")] |
| //! trait TraitSync: DowncastSync {} |
| //! # #[cfg(feature = "sync")] |
| //! impl_downcast!(sync TraitSync); |
| //! |
| //! // With type parameters. |
| //! trait TraitGeneric1<T>: Downcast {} |
| //! impl_downcast!(TraitGeneric1<T>); |
| //! |
| //! // With associated types. |
| //! trait TraitGeneric2: Downcast { type G; type H; } |
| //! impl_downcast!(TraitGeneric2 assoc G, H); |
| //! |
| //! // With constraints on types. |
| //! trait TraitGeneric3<T: Copy>: Downcast { |
| //! type H: Clone; |
| //! } |
| //! impl_downcast!(TraitGeneric3<T> assoc H where T: Copy, H: Clone); |
| //! |
| //! // With concrete types. |
| //! trait TraitConcrete1<T: Copy>: Downcast {} |
| //! impl_downcast!(concrete TraitConcrete1<u32>); |
| //! |
| //! trait TraitConcrete2<T: Copy>: Downcast { type H; } |
| //! impl_downcast!(concrete TraitConcrete2<u32> assoc H=f64); |
| //! # fn main() {} |
| //! ``` |
| //! |
| //! # Example without generics |
| //! |
| //! ```rust |
| //! # use std::rc::Rc; |
| //! # #[cfg(feature = "sync")] |
| //! # use std::sync::Arc; |
| //! # use downcast_rs::impl_downcast; |
| //! # #[cfg(not(feature = "sync"))] |
| //! # use downcast_rs::Downcast; |
| //! # #[cfg(feature = "sync")] |
| //! use downcast_rs::DowncastSync; |
| //! |
| //! // To create a trait with downcasting methods, extend `Downcast` or `DowncastSync` |
| //! // and run `impl_downcast!()` on the trait. |
| //! # #[cfg(not(feature = "sync"))] |
| //! # trait Base: Downcast {} |
| //! # #[cfg(not(feature = "sync"))] |
| //! # impl_downcast!(Base); |
| //! # #[cfg(feature = "sync")] |
| //! trait Base: DowncastSync {} |
| //! # #[cfg(feature = "sync")] |
| //! impl_downcast!(sync Base); // `sync` => also produce `Arc` downcasts. |
| //! |
| //! // Concrete types implementing Base. |
| //! #[derive(Debug)] |
| //! struct Foo(u32); |
| //! impl Base for Foo {} |
| //! #[derive(Debug)] |
| //! struct Bar(f64); |
| //! impl Base for Bar {} |
| //! |
| //! fn main() { |
| //! // Create a trait object. |
| //! let mut base: Box<dyn Base> = Box::new(Foo(42)); |
| //! |
| //! // Try sequential downcasts. |
| //! if let Some(foo) = base.downcast_ref::<Foo>() { |
| //! assert_eq!(foo.0, 42); |
| //! } else if let Some(bar) = base.downcast_ref::<Bar>() { |
| //! assert_eq!(bar.0, 42.0); |
| //! } |
| //! |
| //! assert!(base.is::<Foo>()); |
| //! |
| //! // Fail to convert `Box<dyn Base>` into `Box<Bar>`. |
| //! let res = base.downcast::<Bar>(); |
| //! assert!(res.is_err()); |
| //! let base = res.unwrap_err(); |
| //! // Convert `Box<dyn Base>` into `Box<Foo>`. |
| //! assert_eq!(42, base.downcast::<Foo>().map_err(|_| "Shouldn't happen.").unwrap().0); |
| //! |
| //! // Also works with `Rc`. |
| //! let mut rc: Rc<dyn Base> = Rc::new(Foo(42)); |
| //! assert_eq!(42, rc.downcast_rc::<Foo>().map_err(|_| "Shouldn't happen.").unwrap().0); |
| //! |
| //! // Since this trait is `Sync`, it also supports `Arc` downcasts. |
| //! # #[cfg(feature = "sync")] |
| //! let mut arc: Arc<dyn Base> = Arc::new(Foo(42)); |
| //! # #[cfg(feature = "sync")] |
| //! assert_eq!(42, arc.downcast_arc::<Foo>().map_err(|_| "Shouldn't happen.").unwrap().0); |
| //! } |
| //! ``` |
| //! |
| //! # Example with a generic trait with associated types and constraints |
| //! |
| //! ```rust |
| //! use downcast_rs::{Downcast, impl_downcast}; |
| //! |
| //! // To create a trait with downcasting methods, extend `Downcast` or `DowncastSync` |
| //! // and run `impl_downcast!()` on the trait. |
| //! trait Base<T: Clone>: Downcast { type H: Copy; } |
| //! impl_downcast!(Base<T> assoc H where T: Clone, H: Copy); |
| //! // or: impl_downcast!(concrete Base<u32> assoc H=f32) |
| //! |
| //! // Concrete types implementing Base. |
| //! struct Foo(u32); |
| //! impl Base<u32> for Foo { type H = f32; } |
| //! struct Bar(f64); |
| //! impl Base<u32> for Bar { type H = f32; } |
| //! |
| //! fn main() { |
| //! // Create a trait object. |
| //! let mut base: Box<dyn Base<u32, H=f32>> = Box::new(Bar(42.0)); |
| //! |
| //! // Try sequential downcasts. |
| //! if let Some(foo) = base.downcast_ref::<Foo>() { |
| //! assert_eq!(foo.0, 42); |
| //! } else if let Some(bar) = base.downcast_ref::<Bar>() { |
| //! assert_eq!(bar.0, 42.0); |
| //! } |
| //! |
| //! assert!(base.is::<Bar>()); |
| //! } |
| //! ``` |
| |
| // for compatibility with no std and macros |
| #[doc(hidden)] |
| #[cfg(not(feature = "std"))] |
| pub extern crate core as __std; |
| #[doc(hidden)] |
| #[cfg(feature = "std")] |
| pub extern crate std as __std; |
| #[doc(hidden)] |
| pub extern crate alloc as __alloc; |
| |
| use __std::any::Any; |
| use __alloc::{boxed::Box, rc::Rc}; |
| |
| #[cfg(feature = "sync")] |
| use __alloc::sync::Arc; |
| |
| /// Supports conversion to `Any`. Traits to be extended by `impl_downcast!` must extend `Downcast`. |
| pub trait Downcast: Any { |
| /// Converts `Box<dyn Trait>` (where `Trait: Downcast`) to `Box<dyn Any>`, which can then be |
| /// `downcast` into `Box<dyn ConcreteType>` where `ConcreteType` implements `Trait`. |
| fn into_any(self: Box<Self>) -> Box<dyn Any>; |
| /// Converts `Rc<Trait>` (where `Trait: Downcast`) to `Rc<Any>`, which can then be further |
| /// `downcast` into `Rc<ConcreteType>` where `ConcreteType` implements `Trait`. |
| fn into_any_rc(self: Rc<Self>) -> Rc<dyn Any>; |
| /// Converts `&Trait` (where `Trait: Downcast`) to `&Any`. This is needed since Rust cannot |
| /// generate `&Any`'s vtable from `&Trait`'s. |
| fn as_any(&self) -> &dyn Any; |
| /// Converts `&mut Trait` (where `Trait: Downcast`) to `&Any`. This is needed since Rust cannot |
| /// generate `&mut Any`'s vtable from `&mut Trait`'s. |
| fn as_any_mut(&mut self) -> &mut dyn Any; |
| } |
| |
| impl<T: Any> Downcast for T { |
| fn into_any(self: Box<Self>) -> Box<dyn Any> { self } |
| fn into_any_rc(self: Rc<Self>) -> Rc<dyn Any> { self } |
| fn as_any(&self) -> &dyn Any { self } |
| fn as_any_mut(&mut self) -> &mut dyn Any { self } |
| } |
| |
| /// Extends `Downcast` for `Send` traits to support upcasting to `Box<dyn Any + Send>` as well. |
| pub trait DowncastSend: Downcast + Send { |
| /// Converts `Box<Trait>` (where `Trait: DowncastSend`) to `Box<dyn Any + Send>`, which |
| /// can then be `downcast` into `Box<ConcreteType>` where `ConcreteType` implements `Trait`. |
| fn into_any_send(self: Box<Self>) -> Box<dyn Any + Send>; |
| } |
| |
| impl<T: Any + Send> DowncastSend for T { |
| fn into_any_send(self: Box<Self>) -> Box<dyn Any + Send> { self } |
| } |
| |
| #[cfg(feature = "sync")] |
| /// Extends `DowncastSend` for `Sync` traits to support upcasting to `Box<dyn Any + Send + Sync>` |
| /// and `Arc` downcasting. |
| pub trait DowncastSync: DowncastSend + Sync { |
| /// Converts `Box<Trait>` (where `Trait: DowncastSync`) to `Box<dyn Any + Send + Sync>`, |
| /// which can then be `downcast` into `Box<ConcreteType>` where `ConcreteType` implements |
| /// `Trait`. |
| fn into_any_sync(self: Box<Self>) -> Box<dyn Any + Send + Sync>; |
| /// Converts `Arc<Trait>` (where `Trait: DowncastSync`) to `Arc<Any>`, which can then be |
| /// `downcast` into `Arc<ConcreteType>` where `ConcreteType` implements `Trait`. |
| fn into_any_arc(self: Arc<Self>) -> Arc<dyn Any + Send + Sync>; |
| } |
| |
| #[cfg(feature = "sync")] |
| impl<T: Any + Send + Sync> DowncastSync for T { |
| fn into_any_sync(self: Box<Self>) -> Box<dyn Any + Send + Sync> { self } |
| fn into_any_arc(self: Arc<Self>) -> Arc<dyn Any + Send + Sync> { self } |
| } |
| |
| /// Adds downcasting support to traits that extend `Downcast` by defining forwarding |
| /// methods to the corresponding implementations on `std::any::Any` in the standard library. |
| /// |
| /// See <https://users.rust-lang.org/t/how-to-create-a-macro-to-impl-a-provided-type-parametrized-trait/5289> |
| /// for why this is implemented this way to support templatized traits. |
| #[macro_export(local_inner_macros)] |
| macro_rules! impl_downcast { |
| (@impl_full |
| $trait_:ident [$($param_types:tt)*] |
| for [$($forall_types:ident),*] |
| where [$($preds:tt)*] |
| ) => { |
| impl_downcast! { |
| @inject_where |
| [impl<$($forall_types),*> dyn $trait_<$($param_types)*>] |
| types [$($forall_types),*] |
| where [$($preds)*] |
| [{ |
| impl_downcast! { @impl_body $trait_ [$($param_types)*] } |
| }] |
| } |
| }; |
| |
| (@impl_full_sync |
| $trait_:ident [$($param_types:tt)*] |
| for [$($forall_types:ident),*] |
| where [$($preds:tt)*] |
| ) => { |
| impl_downcast! { |
| @inject_where |
| [impl<$($forall_types),*> dyn $trait_<$($param_types)*>] |
| types [$($forall_types),*] |
| where [$($preds)*] |
| [{ |
| impl_downcast! { @impl_body $trait_ [$($param_types)*] } |
| impl_downcast! { @impl_body_sync $trait_ [$($param_types)*] } |
| }] |
| } |
| }; |
| |
| (@impl_body $trait_:ident [$($types:tt)*]) => { |
| /// Returns true if the trait object wraps an object of type `__T`. |
| #[inline] |
| pub fn is<__T: $trait_<$($types)*>>(&self) -> bool { |
| $crate::Downcast::as_any(self).is::<__T>() |
| } |
| /// Returns a boxed object from a boxed trait object if the underlying object is of type |
| /// `__T`. Returns the original boxed trait if it isn't. |
| #[inline] |
| pub fn downcast<__T: $trait_<$($types)*>>( |
| self: $crate::__alloc::boxed::Box<Self> |
| ) -> $crate::__std::result::Result<$crate::__alloc::boxed::Box<__T>, $crate::__alloc::boxed::Box<Self>> { |
| if self.is::<__T>() { |
| Ok($crate::Downcast::into_any(self).downcast::<__T>().unwrap()) |
| } else { |
| Err(self) |
| } |
| } |
| /// Returns an `Rc`-ed object from an `Rc`-ed trait object if the underlying object is of |
| /// type `__T`. Returns the original `Rc`-ed trait if it isn't. |
| #[inline] |
| pub fn downcast_rc<__T: $trait_<$($types)*>>( |
| self: $crate::__alloc::rc::Rc<Self> |
| ) -> $crate::__std::result::Result<$crate::__alloc::rc::Rc<__T>, $crate::__alloc::rc::Rc<Self>> { |
| if self.is::<__T>() { |
| Ok($crate::Downcast::into_any_rc(self).downcast::<__T>().unwrap()) |
| } else { |
| Err(self) |
| } |
| } |
| /// Returns a reference to the object within the trait object if it is of type `__T`, or |
| /// `None` if it isn't. |
| #[inline] |
| pub fn downcast_ref<__T: $trait_<$($types)*>>(&self) -> $crate::__std::option::Option<&__T> { |
| $crate::Downcast::as_any(self).downcast_ref::<__T>() |
| } |
| /// Returns a mutable reference to the object within the trait object if it is of type |
| /// `__T`, or `None` if it isn't. |
| #[inline] |
| pub fn downcast_mut<__T: $trait_<$($types)*>>(&mut self) -> $crate::__std::option::Option<&mut __T> { |
| $crate::Downcast::as_any_mut(self).downcast_mut::<__T>() |
| } |
| }; |
| |
| (@impl_body_sync $trait_:ident [$($types:tt)*]) => { |
| /// Returns an `Arc`-ed object from an `Arc`-ed trait object if the underlying object is of |
| /// type `__T`. Returns the original `Arc`-ed trait if it isn't. |
| #[inline] |
| pub fn downcast_arc<__T: $trait_<$($types)*> + $crate::__std::any::Any + $crate::__std::marker::Send + $crate::__std::marker::Sync>( |
| self: $crate::__alloc::sync::Arc<Self>, |
| ) -> $crate::__std::result::Result<$crate::__alloc::sync::Arc<__T>, $crate::__alloc::sync::Arc<Self>> |
| { |
| if self.is::<__T>() { |
| Ok($crate::DowncastSync::into_any_arc(self).downcast::<__T>().unwrap()) |
| } else { |
| Err(self) |
| } |
| } |
| }; |
| |
| (@inject_where [$($before:tt)*] types [] where [] [$($after:tt)*]) => { |
| impl_downcast! { @as_item $($before)* $($after)* } |
| }; |
| |
| (@inject_where [$($before:tt)*] types [$($types:ident),*] where [] [$($after:tt)*]) => { |
| impl_downcast! { |
| @as_item |
| $($before)* |
| where $( $types: $crate::__std::any::Any + 'static ),* |
| $($after)* |
| } |
| }; |
| (@inject_where [$($before:tt)*] types [$($types:ident),*] where [$($preds:tt)+] [$($after:tt)*]) => { |
| impl_downcast! { |
| @as_item |
| $($before)* |
| where |
| $( $types: $crate::__std::any::Any + 'static, )* |
| $($preds)* |
| $($after)* |
| } |
| }; |
| |
| (@as_item $i:item) => { $i }; |
| |
| // No type parameters. |
| ($trait_:ident ) => { impl_downcast! { @impl_full $trait_ [] for [] where [] } }; |
| ($trait_:ident <>) => { impl_downcast! { @impl_full $trait_ [] for [] where [] } }; |
| (sync $trait_:ident ) => { impl_downcast! { @impl_full_sync $trait_ [] for [] where [] } }; |
| (sync $trait_:ident <>) => { impl_downcast! { @impl_full_sync $trait_ [] for [] where [] } }; |
| // Type parameters. |
| ($trait_:ident < $($types:ident),* >) => { |
| impl_downcast! { @impl_full $trait_ [$($types),*] for [$($types),*] where [] } |
| }; |
| (sync $trait_:ident < $($types:ident),* >) => { |
| impl_downcast! { @impl_full_sync $trait_ [$($types),*] for [$($types),*] where [] } |
| }; |
| // Type parameters and where clauses. |
| ($trait_:ident < $($types:ident),* > where $($preds:tt)+) => { |
| impl_downcast! { @impl_full $trait_ [$($types),*] for [$($types),*] where [$($preds)*] } |
| }; |
| (sync $trait_:ident < $($types:ident),* > where $($preds:tt)+) => { |
| impl_downcast! { @impl_full_sync $trait_ [$($types),*] for [$($types),*] where [$($preds)*] } |
| }; |
| // Associated types. |
| ($trait_:ident assoc $($atypes:ident),*) => { |
| impl_downcast! { @impl_full $trait_ [$($atypes = $atypes),*] for [$($atypes),*] where [] } |
| }; |
| (sync $trait_:ident assoc $($atypes:ident),*) => { |
| impl_downcast! { @impl_full_sync $trait_ [$($atypes = $atypes),*] for [$($atypes),*] where [] } |
| }; |
| // Associated types and where clauses. |
| ($trait_:ident assoc $($atypes:ident),* where $($preds:tt)+) => { |
| impl_downcast! { @impl_full $trait_ [$($atypes = $atypes),*] for [$($atypes),*] where [$($preds)*] } |
| }; |
| (sync $trait_:ident assoc $($atypes:ident),* where $($preds:tt)+) => { |
| impl_downcast! { @impl_full_sync $trait_ [$($atypes = $atypes),*] for [$($atypes),*] where [$($preds)*] } |
| }; |
| // Type parameters and associated types. |
| ($trait_:ident < $($types:ident),* > assoc $($atypes:ident),*) => { |
| impl_downcast! { |
| @impl_full |
| $trait_ [$($types),*, $($atypes = $atypes),*] |
| for [$($types),*, $($atypes),*] |
| where [] |
| } |
| }; |
| (sync $trait_:ident < $($types:ident),* > assoc $($atypes:ident),*) => { |
| impl_downcast! { |
| @impl_full_sync |
| $trait_ [$($types),*, $($atypes = $atypes),*] |
| for [$($types),*, $($atypes),*] |
| where [] |
| } |
| }; |
| // Type parameters, associated types, and where clauses. |
| ($trait_:ident < $($types:ident),* > assoc $($atypes:ident),* where $($preds:tt)+) => { |
| impl_downcast! { |
| @impl_full |
| $trait_ [$($types),*, $($atypes = $atypes),*] |
| for [$($types),*, $($atypes),*] |
| where [$($preds)*] |
| } |
| }; |
| (sync $trait_:ident < $($types:ident),* > assoc $($atypes:ident),* where $($preds:tt)+) => { |
| impl_downcast! { |
| @impl_full_sync |
| $trait_ [$($types),*, $($atypes = $atypes),*] |
| for [$($types),*, $($atypes),*] |
| where [$($preds)*] |
| } |
| }; |
| // Concretely-parametrized types. |
| (concrete $trait_:ident < $($types:ident),* >) => { |
| impl_downcast! { @impl_full $trait_ [$($types),*] for [] where [] } |
| }; |
| (sync concrete $trait_:ident < $($types:ident),* >) => { |
| impl_downcast! { @impl_full_sync $trait_ [$($types),*] for [] where [] } |
| }; |
| // Concretely-associated types types. |
| (concrete $trait_:ident assoc $($atypes:ident = $aty:ty),*) => { |
| impl_downcast! { @impl_full $trait_ [$($atypes = $aty),*] for [] where [] } |
| }; |
| (sync concrete $trait_:ident assoc $($atypes:ident = $aty:ty),*) => { |
| impl_downcast! { @impl_full_sync $trait_ [$($atypes = $aty),*] for [] where [] } |
| }; |
| // Concretely-parametrized types with concrete associated types. |
| (concrete $trait_:ident < $($types:ident),* > assoc $($atypes:ident = $aty:ty),*) => { |
| impl_downcast! { @impl_full $trait_ [$($types),*, $($atypes = $aty),*] for [] where [] } |
| }; |
| (sync concrete $trait_:ident < $($types:ident),* > assoc $($atypes:ident = $aty:ty),*) => { |
| impl_downcast! { @impl_full_sync $trait_ [$($types),*, $($atypes = $aty),*] for [] where [] } |
| }; |
| } |
| |
| |
| #[cfg(all(test, feature = "sync"))] |
| mod test { |
| /// Substitutes `Downcast` in the body with `DowncastSend`. |
| macro_rules! subst_downcast_send { |
| (@impl { $($parsed:tt)* }, {}) => { $($parsed)* }; |
| (@impl { $($parsed:tt)* }, { Downcast $($rest:tt)* }) => { |
| subst_downcast_send!(@impl { $($parsed)* DowncastSend }, { $($rest)* }); |
| }; |
| (@impl { $($parsed:tt)* }, { $first:tt $($rest:tt)* }) => { |
| subst_downcast_send!(@impl { $($parsed)* $first }, { $($rest)* }); |
| }; |
| ($($body:tt)+) => { |
| subst_downcast_send!(@impl {}, { $($body)* }); |
| }; |
| } |
| |
| macro_rules! test_mod { |
| ( |
| $test_mod_name:ident, |
| trait $base_trait:path { $($base_impl:tt)* }, |
| non_sync: { $($non_sync_def:tt)+ }, |
| sync: { $($sync_def:tt)+ } |
| ) => { |
| test_mod! { |
| $test_mod_name, |
| trait $base_trait { $($base_impl:tt)* }, |
| type dyn $base_trait, |
| non_sync: { $($non_sync_def)* }, |
| sync: { $($sync_def)* } |
| } |
| }; |
| |
| ( |
| $test_mod_name:ident, |
| trait $base_trait:path { $($base_impl:tt)* }, |
| type $base_type:ty, |
| non_sync: { $($non_sync_def:tt)+ }, |
| sync: { $($sync_def:tt)+ } |
| ) => { |
| mod $test_mod_name { |
| // Downcast |
| test_mod!( |
| @test |
| $test_mod_name, |
| test_name: test_non_sync, |
| trait $base_trait { $($base_impl)* }, |
| type $base_type, |
| { $($non_sync_def)+ }, |
| []); |
| |
| // DowncastSend |
| test_mod!( |
| @test |
| $test_mod_name, |
| test_name: test_send, |
| trait $base_trait { $($base_impl)* }, |
| type $base_type, |
| { subst_downcast_send! { $($non_sync_def)+ } }, |
| [{ |
| // Downcast to include Send. |
| let base: $crate::__alloc::boxed::Box<$base_type> = $crate::__alloc::boxed::Box::new(Foo(42)); |
| fn impls_send<T: ::std::marker::Send>(_a: T) {} |
| impls_send(base.into_any_send()); |
| }]); |
| |
| // DowncastSync |
| test_mod!( |
| @test |
| $test_mod_name, |
| test_name: test_sync, |
| trait $base_trait { $($base_impl)* }, |
| type $base_type, |
| { $($sync_def)+ }, |
| [{ |
| // Downcast to include Send. |
| let base: $crate::__alloc::boxed::Box<$base_type> = $crate::__alloc::boxed::Box::new(Foo(42)); |
| fn impls_send<T: ::std::marker::Send>(_a: T) {} |
| impls_send(base.into_any_send()); |
| // Downcast to include Send + Sync. |
| let base: $crate::__alloc::boxed::Box<$base_type> = $crate::__alloc::boxed::Box::new(Foo(42)); |
| fn impls_send_sync<T: ::std::marker::Send + ::std::marker::Sync>(_a: T) {} |
| impls_send_sync(base.into_any_sync()); |
| |
| // Fail to convert Arc<dyn Base> into Arc<Bar>. |
| let arc: $crate::__alloc::sync::Arc<$base_type> = $crate::__alloc::sync::Arc::new(Foo(42)); |
| let res = arc.downcast_arc::<Bar>(); |
| assert!(res.is_err()); |
| let arc = res.unwrap_err(); |
| // Convert Arc<dyn Base> into Arc<Foo>. |
| assert_eq!( |
| 42, arc.downcast_arc::<Foo>().map_err(|_| "Shouldn't happen.").unwrap().0); |
| }]); |
| } |
| }; |
| |
| ( |
| @test |
| $test_mod_name:ident, |
| test_name: $test_name:ident, |
| trait $base_trait:path { $($base_impl:tt)* }, |
| type $base_type:ty, |
| { $($def:tt)+ }, |
| [ $($more_tests:block)* ] |
| ) => { |
| #[test] |
| fn $test_name() { |
| #[allow(unused_imports)] |
| use super::super::{Downcast, DowncastSend, DowncastSync}; |
| |
| // Should work even if standard objects (especially those in the prelude) are |
| // aliased to something else. |
| #[allow(dead_code)] struct Any; |
| #[allow(dead_code)] struct Arc; |
| #[allow(dead_code)] struct Box; |
| #[allow(dead_code)] struct Option; |
| #[allow(dead_code)] struct Result; |
| #[allow(dead_code)] struct Rc; |
| #[allow(dead_code)] struct Send; |
| #[allow(dead_code)] struct Sync; |
| |
| // A trait that can be downcast. |
| $($def)* |
| |
| // Concrete type implementing Base. |
| #[derive(Debug)] |
| struct Foo(u32); |
| impl $base_trait for Foo { $($base_impl)* } |
| #[derive(Debug)] |
| struct Bar(f64); |
| impl $base_trait for Bar { $($base_impl)* } |
| |
| // Functions that can work on references to Base trait objects. |
| fn get_val(base: &$crate::__alloc::boxed::Box<$base_type>) -> u32 { |
| match base.downcast_ref::<Foo>() { |
| Some(val) => val.0, |
| None => 0 |
| } |
| } |
| fn set_val(base: &mut $crate::__alloc::boxed::Box<$base_type>, val: u32) { |
| if let Some(foo) = base.downcast_mut::<Foo>() { |
| foo.0 = val; |
| } |
| } |
| |
| let mut base: $crate::__alloc::boxed::Box<$base_type> = $crate::__alloc::boxed::Box::new(Foo(42)); |
| assert_eq!(get_val(&base), 42); |
| |
| // Try sequential downcasts. |
| if let Some(foo) = base.downcast_ref::<Foo>() { |
| assert_eq!(foo.0, 42); |
| } else if let Some(bar) = base.downcast_ref::<Bar>() { |
| assert_eq!(bar.0, 42.0); |
| } |
| |
| set_val(&mut base, 6*9); |
| assert_eq!(get_val(&base), 6*9); |
| |
| assert!(base.is::<Foo>()); |
| |
| // Fail to convert Box<dyn Base> into Box<Bar>. |
| let res = base.downcast::<Bar>(); |
| assert!(res.is_err()); |
| let base = res.unwrap_err(); |
| // Convert Box<dyn Base> into Box<Foo>. |
| assert_eq!( |
| 6*9, base.downcast::<Foo>().map_err(|_| "Shouldn't happen.").unwrap().0); |
| |
| // Fail to convert Rc<dyn Base> into Rc<Bar>. |
| let rc: $crate::__alloc::rc::Rc<$base_type> = $crate::__alloc::rc::Rc::new(Foo(42)); |
| let res = rc.downcast_rc::<Bar>(); |
| assert!(res.is_err()); |
| let rc = res.unwrap_err(); |
| // Convert Rc<dyn Base> into Rc<Foo>. |
| assert_eq!( |
| 42, rc.downcast_rc::<Foo>().map_err(|_| "Shouldn't happen.").unwrap().0); |
| |
| $($more_tests)* |
| } |
| }; |
| ( |
| $test_mod_name:ident, |
| trait $base_trait:path { $($base_impl:tt)* }, |
| non_sync: { $($non_sync_def:tt)+ }, |
| sync: { $($sync_def:tt)+ } |
| ) => { |
| test_mod! { |
| $test_mod_name, |
| trait $base_trait { $($base_impl:tt)* }, |
| type $base_trait, |
| non_sync: { $($non_sync_def)* }, |
| sync: { $($sync_def)* } |
| } |
| }; |
| |
| } |
| |
| test_mod!(non_generic, trait Base {}, |
| non_sync: { |
| trait Base: Downcast {} |
| impl_downcast!(Base); |
| }, |
| sync: { |
| trait Base: DowncastSync {} |
| impl_downcast!(sync Base); |
| }); |
| |
| test_mod!(generic, trait Base<u32> {}, |
| non_sync: { |
| trait Base<T>: Downcast {} |
| impl_downcast!(Base<T>); |
| }, |
| sync: { |
| trait Base<T>: DowncastSync {} |
| impl_downcast!(sync Base<T>); |
| }); |
| |
| test_mod!(constrained_generic, trait Base<u32> {}, |
| non_sync: { |
| trait Base<T: Copy>: Downcast {} |
| impl_downcast!(Base<T> where T: Copy); |
| }, |
| sync: { |
| trait Base<T: Copy>: DowncastSync {} |
| impl_downcast!(sync Base<T> where T: Copy); |
| }); |
| |
| test_mod!(associated, |
| trait Base { type H = f32; }, |
| type dyn Base<H=f32>, |
| non_sync: { |
| trait Base: Downcast { type H; } |
| impl_downcast!(Base assoc H); |
| }, |
| sync: { |
| trait Base: DowncastSync { type H; } |
| impl_downcast!(sync Base assoc H); |
| }); |
| |
| test_mod!(constrained_associated, |
| trait Base { type H = f32; }, |
| type dyn Base<H=f32>, |
| non_sync: { |
| trait Base: Downcast { type H: Copy; } |
| impl_downcast!(Base assoc H where H: Copy); |
| }, |
| sync: { |
| trait Base: DowncastSync { type H: Copy; } |
| impl_downcast!(sync Base assoc H where H: Copy); |
| }); |
| |
| test_mod!(param_and_associated, |
| trait Base<u32> { type H = f32; }, |
| type dyn Base<u32, H=f32>, |
| non_sync: { |
| trait Base<T>: Downcast { type H; } |
| impl_downcast!(Base<T> assoc H); |
| }, |
| sync: { |
| trait Base<T>: DowncastSync { type H; } |
| impl_downcast!(sync Base<T> assoc H); |
| }); |
| |
| test_mod!(constrained_param_and_associated, |
| trait Base<u32> { type H = f32; }, |
| type dyn Base<u32, H=f32>, |
| non_sync: { |
| trait Base<T: Clone>: Downcast { type H: Copy; } |
| impl_downcast!(Base<T> assoc H where T: Clone, H: Copy); |
| }, |
| sync: { |
| trait Base<T: Clone>: DowncastSync { type H: Copy; } |
| impl_downcast!(sync Base<T> assoc H where T: Clone, H: Copy); |
| }); |
| |
| test_mod!(concrete_parametrized, trait Base<u32> {}, |
| non_sync: { |
| trait Base<T>: Downcast {} |
| impl_downcast!(concrete Base<u32>); |
| }, |
| sync: { |
| trait Base<T>: DowncastSync {} |
| impl_downcast!(sync concrete Base<u32>); |
| }); |
| |
| test_mod!(concrete_associated, |
| trait Base { type H = u32; }, |
| type dyn Base<H=u32>, |
| non_sync: { |
| trait Base: Downcast { type H; } |
| impl_downcast!(concrete Base assoc H=u32); |
| }, |
| sync: { |
| trait Base: DowncastSync { type H; } |
| impl_downcast!(sync concrete Base assoc H=u32); |
| }); |
| |
| test_mod!(concrete_parametrized_associated, |
| trait Base<u32> { type H = f32; }, |
| type dyn Base<u32, H=f32>, |
| non_sync: { |
| trait Base<T>: Downcast { type H; } |
| impl_downcast!(concrete Base<u32> assoc H=f32); |
| }, |
| sync: { |
| trait Base<T>: DowncastSync { type H; } |
| impl_downcast!(sync concrete Base<u32> assoc H=f32); |
| }); |
| } |
