fix(engine): no field type refs for generic types deriving Reflection

3 files changed, 78 insertions, 36 deletions

diff --git a/engine-macros/src/reflection/enum_impl.rs b/engine-macros/src/reflection/enum_impl.rs
index b2e01e8..1760f40 100644
--- a/engine-macros/src/reflection/enum_impl.rs
+++ b/engine-macros/src/reflection/enum_impl.rs
@@ -288,6 +288,10 @@ fn generate_variants<'a>(
                                         unreachable!();
                                     }
                                 },
+                                type_reflection_optional: input
+                                    .generics
+                                    .params
+                                    .is_empty(),
                             },
                         )
                     },
@@ -333,6 +337,10 @@ fn generate_variants<'a>(
                                         }
                                     }
                                 },
+                                type_reflection_optional: input
+                                    .generics
+                                    .params
+                                    .is_empty(),
                             },
                         )
                     },
diff --git a/engine-macros/src/reflection/field.rs b/engine-macros/src/reflection/field.rs
index 7d4e301..95671c3 100644
--- a/engine-macros/src/reflection/field.rs
+++ b/engine-macros/src/reflection/field.rs
@@ -6,6 +6,7 @@ pub struct ReflectionFieldGenOptions<'a>
 {
     pub field_vis_override: Option<syn::Visibility>,
     pub gen_get_byte_offset: &'a dyn Fn(&syn::Field) -> proc_macro2::TokenStream,
+    pub type_reflection_optional: bool,
 }
 
 pub fn generate(
@@ -33,6 +34,12 @@ pub fn generate(
 
     let field_reflection_vis = generate_visibility(field_vis, &engine_crate_path);
 
+    let get_type_fn_body = if options.type_reflection_optional {
+        gen_get_optional_type_reflection(field_type, engine_crate_path)
+    } else {
+        gen_get_mandatory_type_reflection(field_type, engine_crate_path)
+    };
+
     quote! {
         #engine_crate_path::reflection::Field {
             name: #field_name,
@@ -44,44 +51,70 @@ pub fn generate(
                 std::any::type_name::<#field_type>()
             }),
             get_type: #engine_crate_path::reflection::FnWithDebug::new(|| {
-                struct SpecializationTarget<Field>(std::marker::PhantomData<Field>);
-
-                trait FieldHasReflection
-                {
-                    fn field_type_reflection(&self)
-                        -> Option<&'static #engine_crate_path::reflection::Type>;
-                }
-
-                trait FieldDoesNotHaveReflection
-                {
-                    fn field_type_reflection(&self)
-                        -> Option<&'static #engine_crate_path::reflection::Type>;
-                }
-
-                impl<Field> FieldDoesNotHaveReflection for &SpecializationTarget<Field>
-                {
-                    fn field_type_reflection(&self)
-                        -> Option<&'static #engine_crate_path::reflection::Type>
-                    {
-                        None
-                    }
-                }
-
-                impl<Field> FieldHasReflection for SpecializationTarget<Field>
-                where
-                    Field: #engine_crate_path::reflection::Reflection
-                {
-                    fn field_type_reflection(&self)
-                        -> Option<&'static #engine_crate_path::reflection::Type>
-                    {
-                        Some(Field::type_reflection())
-                    }
-                }
-
-                (&SpecializationTarget::<#field_type>(std::marker::PhantomData))
-                    .field_type_reflection()
+                #get_type_fn_body
             }),
             visibility: #field_reflection_vis
         }
     }
 }
+
+fn gen_get_optional_type_reflection(
+    field_type: &syn::Type,
+    engine_crate_path: &syn::Path,
+) -> proc_macro2::TokenStream
+{
+    quote! {
+        struct SpecializationTarget<Field>(std::marker::PhantomData<Field>);
+
+        trait FieldHasReflection
+        {
+            fn field_type_reflection(&self)
+                -> Option<&'static #engine_crate_path::reflection::Type>;
+        }
+
+        trait FieldDoesNotHaveReflection
+        {
+            fn field_type_reflection(&self)
+                -> Option<&'static #engine_crate_path::reflection::Type>;
+        }
+
+        impl<Field> FieldDoesNotHaveReflection for &SpecializationTarget<Field>
+        {
+            fn field_type_reflection(&self)
+                -> Option<&'static #engine_crate_path::reflection::Type>
+            {
+                None
+            }
+        }
+
+        impl<Field> FieldHasReflection for SpecializationTarget<Field>
+        where
+            Field: #engine_crate_path::reflection::Reflection
+        {
+            fn field_type_reflection(&self)
+                -> Option<&'static #engine_crate_path::reflection::Type>
+            {
+                Some(Field::type_reflection())
+            }
+        }
+
+        (&SpecializationTarget::<#field_type>(std::marker::PhantomData))
+            .field_type_reflection()
+    }
+}
+
+fn gen_get_mandatory_type_reflection(
+    field_type: &syn::Type,
+    engine_crate_path: &syn::Path,
+) -> proc_macro2::TokenStream
+{
+    quote! {
+        fn field_type_reflection<T: #engine_crate_path::reflection::Reflection>()
+            -> &'static #engine_crate_path::reflection::Type
+        {
+            T::type_reflection()
+        }
+
+        Some(field_type_reflection::<#field_type>())
+    }
+}
diff --git a/engine-macros/src/reflection/struct_impl.rs b/engine-macros/src/reflection/struct_impl.rs
index 92cf00b..2a271e0 100644
--- a/engine-macros/src/reflection/struct_impl.rs
+++ b/engine-macros/src/reflection/struct_impl.rs
@@ -29,6 +29,7 @@ pub fn generate(input: syn::ItemStruct) -> proc_macro2::TokenStream
                             quote! { std::mem::offset_of!(Self, #field_index) }
                         }
                     },
+                    type_reflection_optional: input.generics.params.is_empty(),
                 },
             )
         });