From 23c4199cac2ce8c0c91ac1e3d9b46fcc1ff72d7a Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Fri, 3 Jul 2026 21:13:09 +0200
Subject: feat(engine): make enum variant field offsets in reflection not
 absolute

---
 engine-macros/src/reflection/enum_impl.rs |  8 --------
 engine-reflection/src/lib.rs              | 26 +++++++++++++++-----------
 2 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/engine-macros/src/reflection/enum_impl.rs b/engine-macros/src/reflection/enum_impl.rs
index 41aa673..ea83681 100644
--- a/engine-macros/src/reflection/enum_impl.rs
+++ b/engine-macros/src/reflection/enum_impl.rs
@@ -227,10 +227,6 @@ fn generate_variants<'a>(
                                 gen_get_byte_offset: &|field| {
                                     if let Some(field_ident) = &field.ident {
                                         quote! {
-                                            std::mem::offset_of!(
-                                                #mod_name::Equivalent #generic_args,
-                                                payload.#variant_ident
-                                            ) +
                                             std::mem::offset_of!(
                                                 #mod_name::#variant_fields_struct_ident
                                                     #generic_args,
@@ -274,10 +270,6 @@ fn generate_variants<'a>(
                                             );
 
                                         quote! {
-                                            std::mem::offset_of!(
-                                                #mod_name::Equivalent #generic_args,
-                                                payload.#variant_ident
-                                            ) +
                                             std::mem::offset_of!(
                                                 #mod_name::#variant_fields_struct_ident
                                                     #generic_args,
diff --git a/engine-reflection/src/lib.rs b/engine-reflection/src/lib.rs
index 600c511..9f347fa 100644
--- a/engine-reflection/src/lib.rs
+++ b/engine-reflection/src/lib.rs
@@ -91,14 +91,15 @@ impl Type
     }
 
     #[inline]
-    pub fn cast_dyn_any(&self, ptr: NonNull<c_void>) -> Option<NonNull<dyn Any>> {
+    pub fn cast_dyn_any(&self, ptr: NonNull<c_void>) -> Option<NonNull<dyn Any>>
+    {
         match self {
             Self::Struct(struct_type) => Some((struct_type.cast_dyn_any)(ptr)),
             Self::Enum(enum_type) => Some((enum_type.cast_dyn_any)(ptr)),
             Self::Literal(literal_type) => Some((literal_type.cast_dyn_any)(ptr)),
             Self::Array(array_type) => Some((array_type.cast_dyn_any)(ptr)),
             Self::Reference(ref_type) => Some((ref_type.cast_dyn_any)(ptr)),
-            Self::Slice(_) => None
+            Self::Slice(_) => None,
         }
     }
 }
@@ -108,7 +109,7 @@ pub struct Struct
 {
     pub fields: &'static [Field],
     pub get_default_value: fn() -> Option<DefaultValueFn>,
-    pub cast_dyn_any: CastDynAnyFn
+    pub cast_dyn_any: CastDynAnyFn,
 }
 
 impl Struct
@@ -140,7 +141,7 @@ pub struct Enum
     pub tagged_union: Option<EnumTaggedUnion>,
 
     pub get_default_value: fn() -> Option<DefaultValueFn>,
-    pub cast_dyn_any: CastDynAnyFn
+    pub cast_dyn_any: CastDynAnyFn,
 }
 
 impl Enum
@@ -218,8 +219,11 @@ pub struct Field
     pub index: usize,
     pub layout: Layout,
 
-    /// Byte offset to the field relative to the start of the type containing it. If the
-    /// type containing the field is a enum, this offset will include the enum tag
+    /// Byte offset to the field relative to the start of the type containing it.
+    ///
+    /// If the type containing the field is a enum variant, this offset is relative to
+    /// the payload field of the enum's equivalent tagged union, therefore this offset
+    /// will **NOT** include the enum tag
     pub byte_offset: usize,
 
     pub type_id: TypeId,
@@ -248,7 +252,7 @@ pub struct Array
     pub item_layout: Layout,
     pub get_item_type_name: FnWithDebug<&'static str>,
     pub length: usize,
-    pub cast_dyn_any: CastDynAnyFn
+    pub cast_dyn_any: CastDynAnyFn,
 }
 
 impl Array
@@ -284,7 +288,7 @@ pub struct Literal
     pub ty: LiteralType,
     pub type_name: fn() -> &'static str,
     pub get_default_value: fn() -> Option<DefaultValueFn>,
-    pub cast_dyn_any: CastDynAnyFn
+    pub cast_dyn_any: CastDynAnyFn,
 }
 
 impl Literal
@@ -306,7 +310,7 @@ impl Literal
 pub struct Reference
 {
     pub ty: &'static Type,
-    pub cast_dyn_any: CastDynAnyFn
+    pub cast_dyn_any: CastDynAnyFn,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -392,7 +396,7 @@ unsafe impl<T: Reflection, const LEN: usize> Reflection for [T; LEN]
         item_layout: Layout::new::<T>(),
         get_item_type_name: FnWithDebug::new(|| type_name::<T>()),
         length: LEN,
-        cast_dyn_any: |ptr| ptr.cast::<Self>()
+        cast_dyn_any: |ptr| ptr.cast::<Self>(),
     });
 }
 
@@ -409,7 +413,7 @@ unsafe impl<T: Reflection> Reflection for &'static T
 {
     const TYPE_REFLECTION: &Type = &Type::Reference(Reference {
         ty: T::TYPE_REFLECTION,
-        cast_dyn_any: |ptr| ptr.cast::<Self>()
+        cast_dyn_any: |ptr| ptr.cast::<Self>(),
     });
 }
 
-- 
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