Add reflect_owned (bevyengine#6494)

# Objective

There is no way to gen an owned value of `Reflect`.

## Solution

Add it! This was originally a part of bevyengine#6421, but @MrGVSV asked me to create a separate for it to implement reflect diffing.

---

## Changelog

### Added

- `Reflect::reflect_owned` to get an owned version of `Reflect`.

crates/bevy_reflect/bevy_reflect_derive/src/impls/enums.rs

@@ -264,6 +264,10 @@ pub(crate) fn impl_enum(reflect_enum: &ReflectEnum) -> TokenStream {
                 #bevy_reflect_path::ReflectMut::Enum(self)
             }
 
+            fn reflect_owned(self: Box<Self>) -> #bevy_reflect_path::ReflectOwned {
+                #bevy_reflect_path::ReflectOwned::Enum(self)
+            }
+
             #hash_fn
 
             #partial_eq_fn

crates/bevy_reflect/bevy_reflect_derive/src/impls/structs.rs

@@ -223,6 +223,10 @@ pub(crate) fn impl_struct(reflect_struct: &ReflectStruct) -> TokenStream {
                 #bevy_reflect_path::ReflectMut::Struct(self)
             }
 
+            fn reflect_owned(self: Box<Self>) -> #bevy_reflect_path::ReflectOwned {
+                #bevy_reflect_path::ReflectOwned::Struct(self)
+            }
+
             #hash_fn
 
             #partial_eq_fn

crates/bevy_reflect/bevy_reflect_derive/src/impls/tuple_structs.rs

@@ -184,6 +184,10 @@ pub(crate) fn impl_tuple_struct(reflect_struct: &ReflectStruct) -> TokenStream {
                 #bevy_reflect_path::ReflectMut::TupleStruct(self)
             }
 
+            fn reflect_owned(self: Box<Self>) -> #bevy_reflect_path::ReflectOwned {
+                #bevy_reflect_path::ReflectOwned::TupleStruct(self)
+            }
+
             #hash_fn
 
             #partial_eq_fn

crates/bevy_reflect/bevy_reflect_derive/src/impls/values.rs

@@ -103,6 +103,10 @@ pub(crate) fn impl_value(meta: &ReflectMeta) -> TokenStream {
                 #bevy_reflect_path::ReflectMut::Value(self)
             }
 
+            fn reflect_owned(self: Box<Self>) -> #bevy_reflect_path::ReflectOwned {
+                #bevy_reflect_path::ReflectOwned::Value(self)
+            }
+
             #hash_fn
 
             #partial_eq_fn

crates/bevy_reflect/src/array.rs

@@ -1,5 +1,6 @@
 use crate::{
-    utility::NonGenericTypeInfoCell, DynamicInfo, Reflect, ReflectMut, ReflectRef, TypeInfo, Typed,
+    utility::NonGenericTypeInfoCell, DynamicInfo, Reflect, ReflectMut, ReflectOwned, ReflectRef,
+    TypeInfo, Typed,
 };
 use std::{
     any::{Any, TypeId},
@@ -226,6 +227,11 @@ impl Reflect for DynamicArray {
         ReflectMut::Array(self)
     }
 
+    #[inline]
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Array(self)
+    }
+
     #[inline]
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(self.clone_dynamic())

crates/bevy_reflect/src/enums/dynamic_enum.rs

@@ -1,7 +1,8 @@
 use crate::utility::NonGenericTypeInfoCell;
 use crate::{
     enum_debug, enum_hash, enum_partial_eq, DynamicInfo, DynamicStruct, DynamicTuple, Enum,
-    Reflect, ReflectMut, ReflectRef, Struct, Tuple, TypeInfo, Typed, VariantFieldIter, VariantType,
+    Reflect, ReflectMut, ReflectOwned, ReflectRef, Struct, Tuple, TypeInfo, Typed,
+    VariantFieldIter, VariantType,
 };
 use std::any::Any;
 use std::fmt::Formatter;
@@ -390,6 +391,11 @@ impl Reflect for DynamicEnum {
         ReflectMut::Enum(self)
     }
 
+    #[inline]
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Enum(self)
+    }
+
     #[inline]
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(self.clone_dynamic())

crates/bevy_reflect/src/impls/smallvec.rs

@@ -4,7 +4,7 @@ use std::any::Any;
 use crate::utility::GenericTypeInfoCell;
 use crate::{
     Array, ArrayIter, FromReflect, FromType, GetTypeRegistration, List, ListInfo, Reflect,
-    ReflectFromPtr, ReflectMut, ReflectRef, TypeInfo, TypeRegistration, Typed,
+    ReflectFromPtr, ReflectMut, ReflectOwned, ReflectRef, TypeInfo, TypeRegistration, Typed,
 };
 
 impl<T: smallvec::Array + Send + Sync + 'static> Array for SmallVec<T>
@@ -115,6 +115,10 @@ where
         ReflectMut::List(self)
     }
 
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::List(self)
+    }
+
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(List::clone_dynamic(self))
     }

crates/bevy_reflect/src/impls/std.rs

@@ -1,5 +1,5 @@
 use crate::std_traits::ReflectDefault;
-use crate::{self as bevy_reflect, ReflectFromPtr};
+use crate::{self as bevy_reflect, ReflectFromPtr, ReflectOwned};
 use crate::{
     map_apply, map_partial_eq, Array, ArrayInfo, ArrayIter, DynamicEnum, DynamicMap, Enum,
     EnumInfo, FromReflect, FromType, GetTypeRegistration, List, ListInfo, Map, MapInfo, MapIter,
@@ -270,6 +270,10 @@ impl<T: FromReflect> Reflect for Vec<T> {
         ReflectMut::List(self)
     }
 
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::List(self)
+    }
+
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(List::clone_dynamic(self))
     }
@@ -434,6 +438,10 @@ impl<K: FromReflect + Eq + Hash, V: FromReflect> Reflect for HashMap<K, V> {
         ReflectMut::Map(self)
     }
 
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Map(self)
+    }
+
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(self.clone_dynamic())
     }
@@ -566,6 +574,11 @@ impl<T: Reflect, const N: usize> Reflect for [T; N] {
         ReflectMut::Array(self)
     }
 
+    #[inline]
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Array(self)
+    }
+
     #[inline]
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(self.clone_dynamic())
@@ -678,6 +691,10 @@ impl Reflect for Cow<'static, str> {
         ReflectMut::Value(self)
     }
 
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Value(self)
+    }
+
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(self.clone())
     }
@@ -868,6 +885,10 @@ impl<T: FromReflect> Reflect for Option<T> {
         ReflectMut::Enum(self)
     }
 
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Enum(self)
+    }
+
     #[inline]
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(Enum::clone_dynamic(self))

crates/bevy_reflect/src/list.rs

@@ -3,8 +3,8 @@ use std::fmt::{Debug, Formatter};
 
 use crate::utility::NonGenericTypeInfoCell;
 use crate::{
-    Array, ArrayIter, DynamicArray, DynamicInfo, FromReflect, Reflect, ReflectMut, ReflectRef,
-    TypeInfo, Typed,
+    Array, ArrayIter, DynamicArray, DynamicInfo, FromReflect, Reflect, ReflectMut, ReflectOwned,
+    ReflectRef, TypeInfo, Typed,
 };
 
 /// An ordered, mutable list of [Reflect] items. This corresponds to types like [`std::vec::Vec`].
@@ -246,6 +246,11 @@ impl Reflect for DynamicList {
         ReflectMut::List(self)
     }
 
+    #[inline]
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::List(self)
+    }
+
     #[inline]
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(List::clone_dynamic(self))

crates/bevy_reflect/src/map.rs

@@ -5,7 +5,7 @@ use std::hash::Hash;
 use bevy_utils::{Entry, HashMap};
 
 use crate::utility::NonGenericTypeInfoCell;
-use crate::{DynamicInfo, Reflect, ReflectMut, ReflectRef, TypeInfo, Typed};
+use crate::{DynamicInfo, Reflect, ReflectMut, ReflectOwned, ReflectRef, TypeInfo, Typed};
 
 /// An ordered mapping between [`Reflect`] values.
 ///
@@ -300,6 +300,10 @@ impl Reflect for DynamicMap {
         ReflectMut::Map(self)
     }
 
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Map(self)
+    }
+
     fn clone_value(&self) -> Box<dyn Reflect> {
         Box::new(self.clone_dynamic())
     }

crates/bevy_reflect/src/reflect.rs

@@ -45,6 +45,23 @@ pub enum ReflectMut<'a> {
     Value(&'a mut dyn Reflect),
 }
 
+/// An owned enumeration of "kinds" of reflected type.
+///
+/// Each variant contains a trait object with methods specific to a kind of
+/// type.
+///
+/// A `ReflectOwned` is obtained via [`Reflect::reflect_owned`].
+pub enum ReflectOwned {
+    Struct(Box<dyn Struct>),
+    TupleStruct(Box<dyn TupleStruct>),
+    Tuple(Box<dyn Tuple>),
+    List(Box<dyn List>),
+    Array(Box<dyn Array>),
+    Map(Box<dyn Map>),
+    Enum(Box<dyn Enum>),
+    Value(Box<dyn Reflect>),
+}
+
 /// A reflected Rust type.
 ///
 /// Methods for working with particular kinds of Rust type are available using the [`Array`], [`List`],
@@ -139,6 +156,11 @@ pub trait Reflect: Any + Send + Sync {
     /// See [`ReflectMut`].
     fn reflect_mut(&mut self) -> ReflectMut;
 
+    /// Returns an owned enumeration of "kinds" of type.
+    ///
+    /// See [`ReflectOwned`].
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned;
+
     /// Clones the value as a `Reflect` trait object.
     ///
     /// When deriving `Reflect` for a struct, tuple struct or enum, the value is

crates/bevy_reflect/src/struct_trait.rs

@@ -1,5 +1,7 @@
 use crate::utility::NonGenericTypeInfoCell;
-use crate::{DynamicInfo, NamedField, Reflect, ReflectMut, ReflectRef, TypeInfo, Typed};
+use crate::{
+    DynamicInfo, NamedField, Reflect, ReflectMut, ReflectOwned, ReflectRef, TypeInfo, Typed,
+};
 use bevy_utils::{Entry, HashMap};
 use std::fmt::{Debug, Formatter};
 use std::{
@@ -427,6 +429,11 @@ impl Reflect for DynamicStruct {
         ReflectMut::Struct(self)
     }
 
+    #[inline]
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Struct(self)
+    }
+
     fn apply(&mut self, value: &dyn Reflect) {
         if let ReflectRef::Struct(struct_value) = value.reflect_ref() {
             for (i, value) in struct_value.iter_fields().enumerate() {

crates/bevy_reflect/src/tuple.rs

@@ -1,7 +1,7 @@
 use crate::utility::NonGenericTypeInfoCell;
 use crate::{
-    DynamicInfo, FromReflect, GetTypeRegistration, Reflect, ReflectMut, ReflectRef, TypeInfo,
-    TypeRegistration, Typed, UnnamedField,
+    DynamicInfo, FromReflect, GetTypeRegistration, Reflect, ReflectMut, ReflectOwned, ReflectRef,
+    TypeInfo, TypeRegistration, Typed, UnnamedField,
 };
 use std::any::{Any, TypeId};
 use std::fmt::{Debug, Formatter};
@@ -341,6 +341,11 @@ impl Reflect for DynamicTuple {
         ReflectMut::Tuple(self)
     }
 
+    #[inline]
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::Tuple(self)
+    }
+
     fn apply(&mut self, value: &dyn Reflect) {
         tuple_apply(self, value);
     }
@@ -540,6 +545,10 @@ macro_rules! impl_reflect_tuple {
                 ReflectMut::Tuple(self)
             }
 
+            fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+                ReflectOwned::Tuple(self)
+            }
+
             fn clone_value(&self) -> Box<dyn Reflect> {
                 Box::new(self.clone_dynamic())
             }

crates/bevy_reflect/src/tuple_struct.rs

@@ -1,5 +1,7 @@
 use crate::utility::NonGenericTypeInfoCell;
-use crate::{DynamicInfo, Reflect, ReflectMut, ReflectRef, TypeInfo, Typed, UnnamedField};
+use crate::{
+    DynamicInfo, Reflect, ReflectMut, ReflectOwned, ReflectRef, TypeInfo, Typed, UnnamedField,
+};
 use std::any::{Any, TypeId};
 use std::fmt::{Debug, Formatter};
 use std::slice::Iter;
@@ -330,6 +332,11 @@ impl Reflect for DynamicTupleStruct {
         ReflectMut::TupleStruct(self)
     }
 
+    #[inline]
+    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
+        ReflectOwned::TupleStruct(self)
+    }
+
     fn apply(&mut self, value: &dyn Reflect) {
         if let ReflectRef::TupleStruct(tuple_struct) = value.reflect_ref() {
             for (i, value) in tuple_struct.iter_fields().enumerate() {

crates/bevy_reflect/src/type_info.rs

@@ -23,7 +23,7 @@ use std::any::{Any, TypeId};
 ///
 /// ```
 /// # use std::any::Any;
-/// # use bevy_reflect::{NamedField, Reflect, ReflectMut, ReflectRef, StructInfo, TypeInfo, ValueInfo};
+/// # use bevy_reflect::{NamedField, Reflect, ReflectMut, ReflectOwned, ReflectRef, StructInfo, TypeInfo, ValueInfo};
 /// # use bevy_reflect::utility::NonGenericTypeInfoCell;
 /// use bevy_reflect::Typed;
 ///
@@ -59,6 +59,7 @@ use std::any::{Any, TypeId};
 /// #   fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> { todo!() }
 /// #   fn reflect_ref(&self) -> ReflectRef { todo!() }
 /// #   fn reflect_mut(&mut self) -> ReflectMut { todo!() }
+/// #   fn reflect_owned(self: Box<Self>) -> ReflectOwned { todo!() }
 /// #   fn clone_value(&self) -> Box<dyn Reflect> { todo!() }
 /// # }
 /// ```

crates/bevy_reflect/src/utility.rs

@@ -16,7 +16,7 @@ use std::any::{Any, TypeId};
 ///
 /// ```
 /// # use std::any::Any;
-/// # use bevy_reflect::{NamedField, Reflect, ReflectMut, ReflectRef, StructInfo, Typed, TypeInfo};
+/// # use bevy_reflect::{NamedField, Reflect, ReflectMut, ReflectOwned, ReflectRef, StructInfo, Typed, TypeInfo};
 /// use bevy_reflect::utility::NonGenericTypeInfoCell;
 ///
 /// struct Foo {
@@ -46,6 +46,7 @@ use std::any::{Any, TypeId};
 /// #   fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> { todo!() }
 /// #   fn reflect_ref(&self) -> ReflectRef { todo!() }
 /// #   fn reflect_mut(&mut self) -> ReflectMut { todo!() }
+/// #   fn reflect_owned(self: Box<Self>) -> ReflectOwned { todo!() }
 /// #   fn clone_value(&self) -> Box<dyn Reflect> { todo!() }
 /// # }
 /// ```
@@ -79,7 +80,7 @@ impl NonGenericTypeInfoCell {
 ///
 /// ```
 /// # use std::any::Any;
-/// # use bevy_reflect::{Reflect, ReflectMut, ReflectRef, TupleStructInfo, Typed, TypeInfo, UnnamedField};
+/// # use bevy_reflect::{Reflect, ReflectMut, ReflectOwned, ReflectRef, TupleStructInfo, Typed, TypeInfo, UnnamedField};
 /// use bevy_reflect::utility::GenericTypeInfoCell;
 ///
 /// struct Foo<T: Reflect>(T);
@@ -107,6 +108,7 @@ impl NonGenericTypeInfoCell {
 /// #   fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> { todo!() }
 /// #   fn reflect_ref(&self) -> ReflectRef { todo!() }
 /// #   fn reflect_mut(&mut self) -> ReflectMut { todo!() }
+/// #   fn reflect_owned(self: Box<Self>) -> ReflectOwned { todo!() }
 /// #   fn clone_value(&self) -> Box<dyn Reflect> { todo!() }
 /// # }
 /// ```