diff --git a/src/impls.rs b/src/impls.rs
index 1d46a29632..121bcd9f12 100644
--- a/src/impls.rs
+++ b/src/impls.rs
@@ -818,7 +818,9 @@ const _: () = {
     // private field, and because it is the name it is referred to in the public
     // documentation of `ManuallyDrop::new`, `ManuallyDrop::into_inner`,
     // `ManuallyDrop::take` and `ManuallyDrop::drop`.
-    unsafe impl<T> HasField<value, 0, { crate::ident_id!(value) }> for ManuallyDrop<T> {
+    unsafe impl<T> HasField<value, { crate::STRUCT_VARIANT_ID }, { crate::ident_id!(value) }>
+        for ManuallyDrop<T>
+    {
         type Type = T;
 
         #[inline]
diff --git a/src/lib.rs b/src/lib.rs
index 020cdf5a91..8688181fda 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1089,6 +1089,17 @@ const _: () = unsafe {
     unsafe_impl_known_layout!(T: ?Sized + KnownLayout => #[repr(T::MaybeUninit)] MaybeUninit<T>)
 };
 
+// FIXME(#196, #2856): Eventually, we'll want to support enums variants and
+// union fields being treated uniformly since they behave similarly to each
+// other in terms of projecting validity – specifically, for a type `T` with
+// validity `V`, if `T` is a struct type, then its fields straightforwardly also
+// have validity `V`. By contrast, if `T` is an enum or union type, then
+// validity is not straightforwardly recursive in this way.
+#[doc(hidden)]
+pub const STRUCT_VARIANT_ID: i128 = -1;
+#[doc(hidden)]
+pub const UNION_VARIANT_ID: i128 = -2;
+
 /// Projects a given field from `Self`.
 ///
 /// All implementations of `HasField` for a particular field `f` in `Self`
@@ -1099,12 +1110,16 @@ const _: () = unsafe {
 ///
 /// A field `f` is `HasField` for `Self` if and only if:
 ///
-/// - if `f` has name `n`, `FIELD_ID` is `zerocopy::ident_id!(n)`; otherwise, if
-///   `f` is at index `i`, `FIELD_ID` is `zerocopy::ident_id!(i)`.
+/// - If `Self` is a struct or union type, then `VARIANT_ID` is
+///   `STRUCT_VARIANT_ID` or `UNION_VARIANT_ID` respectively; otherwise, if
+///   `Self` is an enum type, `VARIANT_ID` is the numerical index of the enum
+///   variant in which `f` appears.
+/// - If `f` has name `n`, `FIELD_ID` is `zerocopy::ident_id!(n)`; otherwise,
+///   if `f` is at index `i`, `FIELD_ID` is `zerocopy::ident_id!(i)`.
 /// - `Field` is a type with the same visibility as `f`.
 /// - `Type` has the same type as `f`.
 #[doc(hidden)]
-pub unsafe trait HasField<Field, const VARIANT_ID: u128, const FIELD_ID: u128> {
+pub unsafe trait HasField<Field, const VARIANT_ID: i128, const FIELD_ID: i128> {
     fn only_derive_is_allowed_to_implement_this_trait()
     where
         Self: Sized;
diff --git a/src/pointer/inner.rs b/src/pointer/inner.rs
index a11ba180b8..a9b447dcc8 100644
--- a/src/pointer/inner.rs
+++ b/src/pointer/inner.rs
@@ -200,7 +200,7 @@ impl<'a, T: ?Sized> PtrInner<'a, T> {
     /// Projects a field.
     #[must_use]
     #[inline(always)]
-    pub fn project<F, const VARIANT_ID: u128, const FIELD_ID: u128>(self) -> PtrInner<'a, T::Type>
+    pub fn project<F, const VARIANT_ID: i128, const FIELD_ID: i128>(self) -> PtrInner<'a, T::Type>
     where
         T: HasField<F, VARIANT_ID, FIELD_ID>,
     {
diff --git a/src/util/macro_util.rs b/src/util/macro_util.rs
index ba908b691d..411b3613c2 100644
--- a/src/util/macro_util.rs
+++ b/src/util/macro_util.rs
@@ -553,7 +553,7 @@ macro_rules! ident_id {
 #[inline(always)]
 #[must_use]
 #[allow(clippy::as_conversions, clippy::indexing_slicing, clippy::arithmetic_side_effects)]
-pub const fn hash_name(name: &str) -> u128 {
+pub const fn hash_name(name: &str) -> i128 {
     let name = name.as_bytes();
 
     // We guarantee freedom from hash collisions between any two strings of
@@ -569,7 +569,7 @@ pub const fn hash_name(name: &str) -> u128 {
             i += 1;
         }
 
-        return u128::from_ne_bytes(bytes);
+        return i128::from_ne_bytes(bytes);
     };
 
     // An implementation of FxHasher, although returning a u128. Probably
@@ -584,7 +584,7 @@ pub const fn hash_name(name: &str) -> u128 {
         hash = (hash.rotate_left(5) ^ (name[i] as u128)).wrapping_mul(K);
         i += 1;
     }
-    hash
+    i128::from_ne_bytes(hash.to_ne_bytes())
 }
 
 /// Is a given source a valid instance of `Dst`?
diff --git a/zerocopy-derive/src/enum.rs b/zerocopy-derive/src/enum.rs
index 5898ef61c4..e4231ec61f 100644
--- a/zerocopy-derive/src/enum.rs
+++ b/zerocopy-derive/src/enum.rs
@@ -301,10 +301,10 @@ pub(crate) fn derive_is_bit_valid(
                     // `___ZerocopyRawEnum` has the same layout as `Self`.
                     let slf = unsafe { slf.cast::<___ZerocopyRawEnum #ty_generics>() };
 
-                    slf.project::<_, 0, { #zerocopy_crate::ident_id!(variants) }>()
-                        .project::<_, 0, { #zerocopy_crate::ident_id!(#variants_union_field_ident) }>()
-                        .project::<_, 0, { #zerocopy_crate::ident_id!(value) }>()
-                        .project::<_, 0, { #zerocopy_crate::ident_id!(#variant_struct_field_index) }>()
+                    slf.project::<_, { #zerocopy_crate::STRUCT_VARIANT_ID }, { #zerocopy_crate::ident_id!(variants) }>()
+                        .project::<_, { #zerocopy_crate::UNION_VARIANT_ID }, { #zerocopy_crate::ident_id!(#variants_union_field_ident) }>()
+                        .project::<_, { #zerocopy_crate::STRUCT_VARIANT_ID }, { #zerocopy_crate::ident_id!(value) }>()
+                        .project::<_, { #zerocopy_crate::STRUCT_VARIANT_ID }, { #zerocopy_crate::ident_id!(#variant_struct_field_index) }>()
                 }
             })
             .build()
@@ -455,7 +455,7 @@ pub(crate) fn derive_is_bit_valid(
             //   overall struct.
             let project = #zerocopy_crate::pointer::PtrInner::project::<
                 _,
-                0,
+                { #zerocopy_crate::STRUCT_VARIANT_ID },
                 { #zerocopy_crate::ident_id!(variants) }
             >;
             let variants = unsafe {
diff --git a/zerocopy-derive/src/lib.rs b/zerocopy-derive/src/lib.rs
index 7274fa0fa8..d2c9dfe94e 100644
--- a/zerocopy-derive/src/lib.rs
+++ b/zerocopy-derive/src/lib.rs
@@ -758,14 +758,19 @@ fn derive_has_field_struct_union(
         )
     });
 
-    let has_fields = fields.iter().map(|(_, ident, ty)| {
+    let variant_id: Box<Expr> = match &ast.data {
+        Data::Struct(_) => parse_quote!({ #zerocopy_crate::STRUCT_VARIANT_ID }),
+        Data::Union(_) => parse_quote!({ #zerocopy_crate::UNION_VARIANT_ID }),
+        _ => unreachable!(),
+    };
+
+    let has_fields = fields.iter().map(move |(_, ident, ty)| {
         let field_token = Ident::new(&format!("ẕ{}", ident), ident.span());
         ImplBlockBuilder::new(
             ast,
             data,
             Trait::HasField {
-                // Use `0` to denote the sole 'variant' of structs and unions.
-                variant_id: parse_quote!({ #zerocopy_crate::ident_id!(0) }),
+                variant_id: variant_id.clone(),
                 field: parse_quote!(#field_token),
                 field_id: parse_quote!({ #zerocopy_crate::ident_id!(#ident) }),
             },
@@ -844,7 +849,11 @@ fn derive_try_from_bytes_struct(
                     use #zerocopy_crate::pointer::PtrInner;
 
                     true #(&& {
-                        let project = <Self as #zerocopy_crate::HasField<_, 0, { #zerocopy_crate::ident_id!(#field_names) }>>::project;
+                        let project = <Self as #zerocopy_crate::HasField<
+                            _,
+                            { #zerocopy_crate::STRUCT_VARIANT_ID },
+                            { #zerocopy_crate::ident_id!(#field_names) }
+                        >>::project;
                         // SAFETY:
                         // - `project` is a field projection, and so it
                         //   addresses a subset of the bytes addressed by `slf`
@@ -905,7 +914,11 @@ fn derive_try_from_bytes_union(
                     use #zerocopy_crate::pointer::PtrInner;
 
                     false #(|| {
-                        let project = <Self as #zerocopy_crate::HasField<_, 0, { #zerocopy_crate::ident_id!(#field_names) }>>::project;
+                        let project = <Self as #zerocopy_crate::HasField<
+                            _,
+                            { #zerocopy_crate::UNION_VARIANT_ID },
+                            { #zerocopy_crate::ident_id!(#field_names) }
+                        >>::project;
                         // SAFETY:
                         // - `project` is a field projection, and so it
                         //   addresses a subset of the bytes addressed by `slf`
diff --git a/zerocopy-derive/src/output_tests.rs b/zerocopy-derive/src/output_tests.rs
index 1baa85637d..fb112a051e 100644
--- a/zerocopy-derive/src/output_tests.rs
+++ b/zerocopy-derive/src/output_tests.rs
@@ -431,7 +431,7 @@ fn test_from_bytes_union() {
                     #[automatically_derived]
                     unsafe impl ::zerocopy::HasField<
                         ẕa,
-                        { ::zerocopy::ident_id!(0) },
+                        { ::zerocopy::UNION_VARIANT_ID },
                         { ::zerocopy::ident_id!(a) },
                     > for Foo {
                         fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -727,7 +727,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(0) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -740,7 +740,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(1) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -753,7 +753,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(2) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -766,7 +766,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(3) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -779,7 +779,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(4) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -792,7 +792,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(5) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -808,7 +808,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(6) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -838,7 +838,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ0,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(0) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -873,7 +873,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ1,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(1) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -908,7 +908,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ2,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(2) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -943,7 +943,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ3,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(3) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -978,7 +978,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ4,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(4) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -1013,7 +1013,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ5,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(5) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -1048,7 +1048,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ6,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(6) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -1129,7 +1129,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(0) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -1142,7 +1142,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(1) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -1155,7 +1155,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(2) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -1168,7 +1168,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(3) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -1181,7 +1181,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(4) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -1209,7 +1209,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ0,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(0) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -1244,7 +1244,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ1,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(1) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -1279,7 +1279,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ2,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(2) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -1314,7 +1314,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ3,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(3) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -1349,7 +1349,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ4,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(4) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -1404,7 +1404,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__field_StructLike,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__field_StructLike) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -1438,7 +1438,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__field_TupleLike,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__field_TupleLike) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -1472,7 +1472,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__nonempty,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__nonempty) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -1514,7 +1514,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕtag,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::STRUCT_VARIANT_ID },
                             { ::zerocopy::ident_id!(tag) },
                         > for ___ZerocopyRawEnum<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -1546,7 +1546,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕvariants,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::STRUCT_VARIANT_ID },
                             { ::zerocopy::ident_id!(variants) },
                         > for ___ZerocopyRawEnum<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -1592,10 +1592,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(1) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(1) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -1620,10 +1620,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(2) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(2) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -1648,10 +1648,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(3) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(3) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -1676,10 +1676,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(4) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(4) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -1704,10 +1704,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(5) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(5) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -1732,10 +1732,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(1) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(1) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -1760,10 +1760,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(2) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(2) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -1788,10 +1788,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(3) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(3) }>()
                         }
                     }
                     let tag = {
@@ -1816,7 +1816,7 @@ fn test_try_from_bytes_enum() {
                     let raw_enum = unsafe { raw_enum.assume_initialized() };
                     let project = ::zerocopy::pointer::PtrInner::project::<
                         _,
-                        0,
+                        { ::zerocopy::STRUCT_VARIANT_ID },
                         { ::zerocopy::ident_id!(variants) },
                     >;
                     let variants = unsafe { raw_enum.cast_unsized_unchecked(project) };
@@ -1985,7 +1985,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(0) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -1998,7 +1998,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(1) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2011,7 +2011,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(2) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2024,7 +2024,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(3) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2037,7 +2037,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(4) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2050,7 +2050,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(5) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2066,7 +2066,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(6) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2096,7 +2096,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ0,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(0) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -2131,7 +2131,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ1,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(1) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -2166,7 +2166,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ2,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(2) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -2201,7 +2201,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ3,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(3) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -2236,7 +2236,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ4,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(4) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -2271,7 +2271,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ5,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(5) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -2306,7 +2306,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ6,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(6) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -2387,7 +2387,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(0) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2400,7 +2400,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(1) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2413,7 +2413,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(2) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2426,7 +2426,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(3) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2439,7 +2439,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(4) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -2467,7 +2467,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ0,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(0) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -2502,7 +2502,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ1,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(1) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -2537,7 +2537,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ2,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(2) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -2572,7 +2572,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ3,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(3) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -2607,7 +2607,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ4,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(4) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -2662,7 +2662,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__field_StructLike,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__field_StructLike) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -2696,7 +2696,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__field_TupleLike,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__field_TupleLike) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -2730,7 +2730,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__nonempty,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__nonempty) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -2772,7 +2772,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕtag,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::STRUCT_VARIANT_ID },
                             { ::zerocopy::ident_id!(tag) },
                         > for ___ZerocopyRawEnum<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -2804,7 +2804,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕvariants,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::STRUCT_VARIANT_ID },
                             { ::zerocopy::ident_id!(variants) },
                         > for ___ZerocopyRawEnum<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -2850,10 +2850,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(1) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(1) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -2878,10 +2878,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(2) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(2) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -2906,10 +2906,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(3) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(3) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -2934,10 +2934,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(4) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(4) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -2962,10 +2962,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(5) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(5) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -2990,10 +2990,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(1) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(1) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -3018,10 +3018,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(2) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(2) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -3046,10 +3046,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(3) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(3) }>()
                         }
                     }
                     let tag = {
@@ -3074,7 +3074,7 @@ fn test_try_from_bytes_enum() {
                     let raw_enum = unsafe { raw_enum.assume_initialized() };
                     let project = ::zerocopy::pointer::PtrInner::project::<
                         _,
-                        0,
+                        { ::zerocopy::STRUCT_VARIANT_ID },
                         { ::zerocopy::ident_id!(variants) },
                     >;
                     let variants = unsafe { raw_enum.cast_unsized_unchecked(project) };
@@ -3243,7 +3243,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(0) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3256,7 +3256,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(1) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3269,7 +3269,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(2) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3282,7 +3282,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(3) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3295,7 +3295,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(4) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3308,7 +3308,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(5) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3324,7 +3324,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(6) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3354,7 +3354,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ0,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(0) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -3389,7 +3389,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ1,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(1) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -3424,7 +3424,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ2,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(2) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -3459,7 +3459,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ3,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(3) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -3494,7 +3494,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ4,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(4) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -3529,7 +3529,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ5,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(5) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -3564,7 +3564,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ6,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(6) },
                             > for ___ZerocopyVariantStruct_StructLike<'a, { N }, X, Y>
                             where
@@ -3645,7 +3645,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(0) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3658,7 +3658,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(1) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3671,7 +3671,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(2) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3684,7 +3684,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(3) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3697,7 +3697,7 @@ fn test_try_from_bytes_enum() {
                                     && {
                                         let project = <Self as ::zerocopy::HasField<
                                             _,
-                                            0,
+                                            { ::zerocopy::STRUCT_VARIANT_ID },
                                             { ::zerocopy::ident_id!(4) },
                                         >>::project;
                                         let field_candidate = unsafe {
@@ -3725,7 +3725,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ0,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(0) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -3760,7 +3760,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ1,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(1) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -3795,7 +3795,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ2,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(2) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -3830,7 +3830,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ3,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(3) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -3865,7 +3865,7 @@ fn test_try_from_bytes_enum() {
                                 Y: Deref,
                             > ::zerocopy::HasField<
                                 ẕ4,
-                                { ::zerocopy::ident_id!(0) },
+                                { ::zerocopy::STRUCT_VARIANT_ID },
                                 { ::zerocopy::ident_id!(4) },
                             > for ___ZerocopyVariantStruct_TupleLike<'a, { N }, X, Y>
                             where
@@ -3920,7 +3920,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__field_StructLike,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__field_StructLike) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -3954,7 +3954,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__field_TupleLike,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__field_TupleLike) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -3988,7 +3988,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕ__nonempty,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::UNION_VARIANT_ID },
                             { ::zerocopy::ident_id!(__nonempty) },
                         > for ___ZerocopyVariants<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -4030,7 +4030,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕtag,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::STRUCT_VARIANT_ID },
                             { ::zerocopy::ident_id!(tag) },
                         > for ___ZerocopyRawEnum<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -4062,7 +4062,7 @@ fn test_try_from_bytes_enum() {
                             Y: Deref,
                         > ::zerocopy::HasField<
                             ẕvariants,
-                            { ::zerocopy::ident_id!(0) },
+                            { ::zerocopy::STRUCT_VARIANT_ID },
                             { ::zerocopy::ident_id!(variants) },
                         > for ___ZerocopyRawEnum<'a, { N }, X, Y> {
                             fn only_derive_is_allowed_to_implement_this_trait() {}
@@ -4108,10 +4108,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(1) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(1) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -4136,10 +4136,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(2) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(2) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -4164,10 +4164,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(3) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(3) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -4192,10 +4192,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(4) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(4) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -4220,10 +4220,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_StructLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(5) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_StructLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(5) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -4248,10 +4248,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(1) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(1) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -4276,10 +4276,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(2) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(2) }>()
                         }
                     }
                     #[allow(deprecated, non_local_definitions)]
@@ -4304,10 +4304,10 @@ fn test_try_from_bytes_enum() {
                             slf: ::zerocopy::PtrInner<'_, Self>,
                         ) -> ::zerocopy::PtrInner<'_, Self::Type> {
                             let slf = unsafe { slf.cast::<___ZerocopyRawEnum<'a, N, X, Y>>() };
-                            slf.project::<_, 0, { ::zerocopy::ident_id!(variants) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(__field_TupleLike) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(value) }>()
-                                .project::<_, 0, { ::zerocopy::ident_id!(3) }>()
+                            slf.project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(variants) }>()
+                                .project::<_, { ::zerocopy::UNION_VARIANT_ID }, { ::zerocopy::ident_id!(__field_TupleLike) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(value) }>()
+                                .project::<_, { ::zerocopy::STRUCT_VARIANT_ID }, { ::zerocopy::ident_id!(3) }>()
                         }
                     }
                     let tag = {
@@ -4332,7 +4332,7 @@ fn test_try_from_bytes_enum() {
                     let raw_enum = unsafe { raw_enum.assume_initialized() };
                     let project = ::zerocopy::pointer::PtrInner::project::<
                         _,
-                        0,
+                        { ::zerocopy::STRUCT_VARIANT_ID },
                         { ::zerocopy::ident_id!(variants) },
                     >;
                     let variants = unsafe { raw_enum.cast_unsized_unchecked(project) };