Implement Upcasting without nightly support (#825)

libraries/dyn-any/src/lib.rs

@@ -5,8 +5,49 @@
 #[cfg_attr(feature = "unstable-docs", doc(cfg(feature = "derive")))]
 pub use dyn_any_derive::DynAny;
 
+/// Implement this trait for your `dyn Trait` types for all `T: Trait`
+pub trait UpcastFrom<T: ?Sized> {
+	fn up_from(value: &T) -> &Self;
+	fn up_from_mut(value: &mut T) -> &mut Self;
+	fn up_from_box(value: Box<T>) -> Box<Self>;
+}
+
+/// Use this trait to perform your upcasts on dyn traits. Make sure to require it in the supertrait!
+pub trait Upcast<U: ?Sized> {
+	fn up(&self) -> &U;
+	fn up_mut(&mut self) -> &mut U;
+	fn up_box(self: Box<Self>) -> Box<U>;
+}
+
+impl<T: ?Sized, U: ?Sized> Upcast<U> for T
+where
+	U: UpcastFrom<T>,
+{
+	fn up(&self) -> &U {
+		U::up_from(self)
+	}
+	fn up_mut(&mut self) -> &mut U {
+		U::up_from_mut(self)
+	}
+	fn up_box(self: Box<Self>) -> Box<U> {
+		U::up_from_box(self)
+	}
+}
+
 use std::any::TypeId;
 
+impl<'a, T: DynAny<'a> + 'a> UpcastFrom<T> for dyn DynAny<'a> + 'a {
+	fn up_from(value: &T) -> &(dyn DynAny<'a> + 'a) {
+		value
+	}
+	fn up_from_mut(value: &mut T) -> &mut (dyn DynAny<'a> + 'a) {
+		value
+	}
+	fn up_from_box(value: Box<T>) -> Box<Self> {
+		value
+	}
+}
+
 pub trait DynAny<'a> {
 	fn type_id(&self) -> TypeId;
 }

node-graph/graph-craft/src/document/value.rs

@@ -2,11 +2,11 @@ use dyn_any::StaticType;
 
 use dyn_clone::DynClone;
 
-use dyn_any::DynAny;
+use dyn_any::{DynAny, Upcast};
 
 pub type Value = Box<dyn ValueTrait>;
 
-pub trait ValueTrait: DynAny<'static> + std::fmt::Debug + DynClone {}
+pub trait ValueTrait: DynAny<'static> + Upcast<dyn DynAny<'static>> + std::fmt::Debug + DynClone {}
 
 pub trait IntoValue: Sized + ValueTrait + 'static {
 	fn into_any(self) -> Value {
@@ -14,7 +14,7 @@ pub trait IntoValue: Sized + ValueTrait + 'static {
 	}
 }
 
-impl<T: 'static + StaticType + std::fmt::Debug + PartialEq + Clone> ValueTrait for T {}
+impl<T: 'static + StaticType + Upcast<dyn DynAny<'static>> + std::fmt::Debug + PartialEq + Clone> ValueTrait for T {}
 
 impl<T: 'static + ValueTrait> IntoValue for T {}
 

node-graph/graph-craft/src/lib.rs

@@ -1,4 +1,3 @@
-#![feature(trait_upcasting)]
 pub mod node_registry;
 
 pub mod document;

node-graph/graph-craft/src/node_registry.rs

@@ -13,6 +13,8 @@ use graphene_std::raster::Image;
 use crate::proto::Type;
 use crate::proto::{ConstructionArgs, NodeIdentifier, ProtoNode, ProtoNodeInput, Type::Concrete};
 
+use dyn_any::Upcast;
+
 type NodeConstructor = fn(ProtoNode, &FixedSizeStack<TypeErasedNode<'static>>);
 
 //TODO: turn into hasmap
@@ -186,7 +188,8 @@ static NODE_REGISTRY: &[(NodeIdentifier<'static>, NodeConstructor)] = &[
 		|proto_node, stack| {
 			stack.push_fn(|_nodes| {
 				if let ConstructionArgs::Value(value) = proto_node.construction_args {
-					let node = FnNode::new(move |_| value.clone() as Any<'static>);
+					let node = FnNode::new(move |_| value.clone().up_box() as Any<'static>);
+
 					node.into_type_erased()
 				} else {
 					unreachable!()
@@ -202,7 +205,7 @@ static NODE_REGISTRY: &[(NodeIdentifier<'static>, NodeConstructor)] = &[
 		|proto_node, stack| {
 			stack.push_fn(|_nodes| {
 				if let ConstructionArgs::Value(value) = proto_node.construction_args {
-					let node = FnNode::new(move |_| value.clone() as Any<'static>);
+					let node = FnNode::new(move |_| value.clone().up_box() as Any<'static>);
 					node.into_type_erased()
 				} else {
 					unreachable!()