add Reflect and Typed bounds when reflecting on a struct that has generic types

Author: cbournhonesque-sc

crates/bevy_reflect/bevy_reflect_derive/src/derive_data.rs

@@ -7,7 +7,7 @@ use quote::quote;
 use crate::{utility, REFLECT_ATTRIBUTE_NAME, REFLECT_VALUE_ATTRIBUTE_NAME};
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
-use syn::{Data, DeriveInput, Field, Fields, Generics, Ident, Meta, Path, Token, Variant};
+use syn::{Data, DeriveInput, Field, Fields, Generics, Ident, Meta, Path, Token, Type, Variant};
 
 pub(crate) enum ReflectDerive<'a> {
     Struct(ReflectStruct<'a>),
@@ -322,6 +322,7 @@ impl<'a> ReflectMeta<'a> {
             &self.bevy_reflect_path,
             self.traits.idents(),
             self.generics,
+            &Vec::default(),
             None,
         )
     }
@@ -350,14 +351,15 @@ impl<'a> ReflectStruct<'a> {
     /// Returns the `GetTypeRegistration` impl as a `TokenStream`.
     ///
     /// Returns a specific implementation for structs and this method should be preffered over the generic [`get_type_registration`](crate::ReflectMeta) method
-    pub fn get_type_registration(&self) -> proc_macro2::TokenStream {
+    pub fn get_type_registration(&self, fields: &Vec<Type>) -> proc_macro2::TokenStream {
         let reflect_path = self.meta.bevy_reflect_path();
 
         crate::registration::impl_get_type_registration(
             self.meta.type_name(),
             reflect_path,
             self.meta.traits().idents(),
             self.meta.generics(),
+            fields,
             Some(&self.serialization_denylist),
         )
     }

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

@@ -76,6 +76,7 @@ pub(crate) fn impl_enum(reflect_enum: &ReflectEnum) -> TokenStream {
     let typed_impl = impl_typed(
         enum_name,
         reflect_enum.meta().generics(),
+        &Vec::default(),
         quote! {
             let variants = [#(#variant_info),*];
             let info = #info_generator;

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

@@ -91,6 +91,7 @@ pub(crate) fn impl_struct(reflect_struct: &ReflectStruct) -> TokenStream {
     let typed_impl = impl_typed(
         struct_name,
         reflect_struct.meta().generics(),
+        &field_types,
         quote! {
             let fields = [#field_generator];
             let info = #info_generator;
@@ -99,16 +100,34 @@ pub(crate) fn impl_struct(reflect_struct: &ReflectStruct) -> TokenStream {
         bevy_reflect_path,
     );
 
-    let get_type_registration_impl = reflect_struct.get_type_registration();
+    let get_type_registration_impl = reflect_struct.get_type_registration(&field_types);
     let (impl_generics, ty_generics, where_clause) =
         reflect_struct.meta().generics().split_for_impl();
 
+    // Add Reflect bound for each active field
+    let mut where_reflect_clause = if where_clause.is_some() {
+        quote! {#where_clause}
+    } else if !field_types.is_empty() {
+        quote! {where}
+    } else {
+        quote! {}
+    };
+    where_reflect_clause.extend(quote! {
+        // TODO: had to add #bevy_reflect_path::Typed to get the test to compile,
+        //  presumably because of this:
+        //  #[inline]
+        //  fn get_type_info(&self) -> &'static bevy_reflect::TypeInfo {
+        //      <Self as bevy_reflect::Typed>::type_info()
+        //  }
+        #(#field_types: #bevy_reflect_path::Reflect + #bevy_reflect_path::Typed,)*
+    });
+
     TokenStream::from(quote! {
         #get_type_registration_impl
 
         #typed_impl
 
-        impl #impl_generics #bevy_reflect_path::Struct for #struct_name #ty_generics #where_clause {
+        impl #impl_generics #bevy_reflect_path::Struct for #struct_name #ty_generics #where_reflect_clause {
             fn field(&self, name: &str) -> #FQOption<&dyn #bevy_reflect_path::Reflect> {
                 match name {
                     #(#field_names => #fqoption::Some(&self.#field_idents),)*
@@ -160,7 +179,7 @@ pub(crate) fn impl_struct(reflect_struct: &ReflectStruct) -> TokenStream {
             }
         }
 
-        impl #impl_generics #bevy_reflect_path::Reflect for #struct_name #ty_generics #where_clause {
+        impl #impl_generics #bevy_reflect_path::Reflect for #struct_name #ty_generics #where_reflect_clause {
             #[inline]
             fn type_name(&self) -> &str {
                 ::core::any::type_name::<Self>()

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

@@ -11,7 +11,6 @@ pub(crate) fn impl_tuple_struct(reflect_struct: &ReflectStruct) -> TokenStream {
 
     let bevy_reflect_path = reflect_struct.meta().bevy_reflect_path();
     let struct_name = reflect_struct.meta().type_name();
-    let get_type_registration_impl = reflect_struct.get_type_registration();
 
     let field_idents = reflect_struct
         .active_fields()
@@ -21,6 +20,8 @@ pub(crate) fn impl_tuple_struct(reflect_struct: &ReflectStruct) -> TokenStream {
     let field_count = field_idents.len();
     let field_indices = (0..field_count).collect::<Vec<usize>>();
 
+    let get_type_registration_impl = reflect_struct.get_type_registration(&field_types);
+
     let hash_fn = reflect_struct
         .meta()
         .traits()
@@ -75,6 +76,7 @@ pub(crate) fn impl_tuple_struct(reflect_struct: &ReflectStruct) -> TokenStream {
     let typed_impl = impl_typed(
         struct_name,
         reflect_struct.meta().generics(),
+        &field_types,
         quote! {
             let fields = [#field_generator];
             let info = #info_generator;
@@ -86,12 +88,30 @@ pub(crate) fn impl_tuple_struct(reflect_struct: &ReflectStruct) -> TokenStream {
     let (impl_generics, ty_generics, where_clause) =
         reflect_struct.meta().generics().split_for_impl();
 
+    // Add Reflect bound for each active field
+    let mut where_reflect_clause = if where_clause.is_some() {
+        quote! {#where_clause}
+    } else if !field_types.is_empty() {
+        quote! {where}
+    } else {
+        quote! {}
+    };
+    where_reflect_clause.extend(quote! {
+        // TODO: had to add #bevy_reflect_path::Typed to get the test to compile,
+        //  presumably because of this:
+        //  #[inline]
+        //  fn get_type_info(&self) -> &'static bevy_reflect::TypeInfo {
+        //      <Self as bevy_reflect::Typed>::type_info()
+        //  }
+        #(#field_types: #bevy_reflect_path::Reflect + #bevy_reflect_path::Typed,)*
+    });
+
     TokenStream::from(quote! {
         #get_type_registration_impl
 
         #typed_impl
 
-        impl #impl_generics #bevy_reflect_path::TupleStruct for #struct_name #ty_generics #where_clause {
+        impl #impl_generics #bevy_reflect_path::TupleStruct for #struct_name #ty_generics #where_reflect_clause {
             fn field(&self, index: usize) -> #FQOption<&dyn #bevy_reflect_path::Reflect> {
                 match index {
                     #(#field_indices => #fqoption::Some(&self.#field_idents),)*
@@ -122,7 +142,7 @@ pub(crate) fn impl_tuple_struct(reflect_struct: &ReflectStruct) -> TokenStream {
             }
         }
 
-        impl #impl_generics #bevy_reflect_path::Reflect for #struct_name #ty_generics #where_clause {
+        impl #impl_generics #bevy_reflect_path::Reflect for #struct_name #ty_generics #where_reflect_clause {
             #[inline]
             fn type_name(&self) -> &str {
                 ::core::any::type_name::<Self>()

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

@@ -1,10 +1,11 @@
 use proc_macro2::Ident;
 use quote::quote;
-use syn::{Generics, Path};
+use syn::{Generics, Path, Type};
 
 pub(crate) fn impl_typed(
     type_name: &Ident,
     generics: &Generics,
+    field_types: &Vec<Type>,
     generator: proc_macro2::TokenStream,
     bevy_reflect_path: &Path,
 ) -> proc_macro2::TokenStream {
@@ -28,8 +29,20 @@ pub(crate) fn impl_typed(
 
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
+    // Add Typed bound for each active field
+    let mut where_typed_clause = if where_clause.is_some() {
+        quote! {#where_clause}
+    } else if !field_types.is_empty() {
+        quote! {where}
+    } else {
+        quote! {}
+    };
+    where_typed_clause.extend(quote! {
+        #(#field_types: #bevy_reflect_path::Typed,)*
+    });
+
     quote! {
-        impl #impl_generics #bevy_reflect_path::Typed for #type_name #ty_generics #where_clause {
+        impl #impl_generics #bevy_reflect_path::Typed for #type_name #ty_generics #where_typed_clause {
             fn type_info() -> &'static #bevy_reflect_path::TypeInfo {
                 #static_generator
             }

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

@@ -21,9 +21,11 @@ pub(crate) fn impl_value(meta: &ReflectMeta) -> TokenStream {
     #[cfg(not(feature = "documentation"))]
     let with_docs: Option<proc_macro2::TokenStream> = None;
 
+    let field_types = Vec::default();
     let typed_impl = impl_typed(
         type_name,
         meta.generics(),
+        &field_types,
         quote! {
             let info = #bevy_reflect_path::ValueInfo::new::<Self>() #with_docs;
             #bevy_reflect_path::TypeInfo::Value(info)

crates/bevy_reflect/bevy_reflect_derive/src/registration.rs

@@ -3,14 +3,15 @@
 use bit_set::BitSet;
 use proc_macro2::Ident;
 use quote::quote;
-use syn::{Generics, Path};
+use syn::{Generics, Path, Type};
 
 /// Creates the `GetTypeRegistration` impl for the given type data.
 pub(crate) fn impl_get_type_registration(
     type_name: &Ident,
     bevy_reflect_path: &Path,
     registration_data: &[Ident],
     generics: &Generics,
+    field_types: &Vec<Type>,
     serialization_denylist: Option<&BitSet<u32>>,
 ) -> proc_macro2::TokenStream {
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
@@ -22,9 +23,21 @@ pub(crate) fn impl_get_type_registration(
         }
     });
 
+    // Add Typed bound for each active field
+    let mut where_reflect_typed_clause = if where_clause.is_some() {
+        quote! {#where_clause}
+    } else if !field_types.is_empty() {
+        quote! {where}
+    } else {
+        quote! {}
+    };
+    where_reflect_typed_clause.extend(quote! {
+        #(#field_types: #bevy_reflect_path::Reflect + #bevy_reflect_path::Typed,)*
+    });
+
     quote! {
         #[allow(unused_mut)]
-        impl #impl_generics #bevy_reflect_path::GetTypeRegistration for #type_name #ty_generics #where_clause {
+        impl #impl_generics #bevy_reflect_path::GetTypeRegistration for #type_name #ty_generics #where_reflect_typed_clause {
             fn get_type_registration() -> #bevy_reflect_path::TypeRegistration {
                 let mut registration = #bevy_reflect_path::TypeRegistration::of::<#type_name #ty_generics>();
                 registration.insert::<#bevy_reflect_path::ReflectFromPtr>(#bevy_reflect_path::FromType::<#type_name #ty_generics>::from_type());

crates/bevy_reflect/src/lib.rs

@@ -158,6 +158,32 @@ mod tests {
         assert_eq!(foo.a, 123);
     }
 
+    #[test]
+    fn reflect_struct_generics() {
+        #[derive(Reflect)]
+        struct Foo<T> {
+            a: T,
+        }
+
+        let mut foo = Foo::<u32>{
+            a: 42,
+        };
+
+        let a = *foo.get_field::<u32>("a").unwrap();
+        assert_eq!(a, 42);
+
+        *foo.get_field_mut::<u32>("a").unwrap() += 1;
+        assert_eq!(foo.a, 43);
+
+        // patch Foo with a dynamic struct
+        let mut dynamic_struct = DynamicStruct::default();
+        dynamic_struct.insert("a", 123u32);
+        dynamic_struct.insert("should_be_ignored", 456);
+
+        foo.apply(&dynamic_struct);
+        assert_eq!(foo.a, 123);
+    }
+
     #[test]
     fn reflect_map() {
         #[derive(Reflect, Hash)]