feat: add repr attribute via ast_node attribute.

crates/oxc_macros/src/ast_node.rs

@@ -1,10 +1,9 @@
-use std::slice;
-
 use proc_macro2::TokenStream as TokenStream2;
 
 use quote::quote;
 use syn::{
-    punctuated::Punctuated, Attribute, Generics, Ident, Item, ItemEnum, ItemStruct, Meta, Token,
+    parse_quote, punctuated::Punctuated, Attribute, Generics, Ident, Item, ItemEnum, ItemStruct,
+    Meta, Token,
 };
 
 pub fn ast_node(mut item: Item) -> TokenStream2 {
@@ -25,30 +24,55 @@ pub fn ast_node(mut item: Item) -> TokenStream2 {
 }
 
 fn modify_struct(item: &mut ItemStruct) -> NodeData {
-    validate_struct_attributes(item.attrs.iter());
+    validate_struct_attributes(&item.attrs);
+    item.attrs.push(parse_quote!(#[repr(C)]));
     NodeData { ident: &item.ident, generics: &item.generics }
 }
 
 fn modify_enum(item: &mut ItemEnum) -> NodeData {
-    validate_enum_attributes(item.attrs.iter());
+    validate_enum_attributes(&item.attrs);
+    item.attrs.push(parse_quote!(#[repr(C, u8)]));
     NodeData { ident: &item.ident, generics: &item.generics }
 }
 
-fn validate_struct_attributes<'a>(mut attrs: slice::Iter<'a, Attribute>) {
+fn validate_struct_attributes<I>(attrs: &I)
+where
+    for<'a> &'a I: IntoIterator<Item = &'a Attribute>,
+{
     // make sure that no structure derives Clone/Copy traits.
     // TODO: It will fail if there is a manual Clone/Copy traits implemented for the struct.
     // Negative traits (!Copy and !Clone) are nightly so I'm not sure how we can fully enforce it.
-    assert!(!attrs.any(|attr| {
-        let args = attr.parse_args_with(Punctuated::<Meta, Token![,]>::parse_terminated);
-        attr.path().is_ident("derive")
-            && args.is_ok_and(|args| {
-                args.iter().any(|arg| arg.path().is_ident("Clone") || arg.path().is_ident("Copy"))
-            })
-    }));
+    assert!(
+        !attrs.into_iter().any(|attr| {
+            let args = attr.parse_args_with(Punctuated::<Meta, Token![,]>::parse_terminated);
+            attr.path().is_ident("derive")
+                && args.is_ok_and(|args| {
+                    args.iter()
+                        .any(|arg| arg.path().is_ident("Clone") || arg.path().is_ident("Copy"))
+                })
+        }),
+        "`ast_node` can't have Clone or Copy traits"
+    );
+
+    validate_attributes(attrs);
 }
 
-fn validate_enum_attributes<'a>(_: slice::Iter<'a, Attribute>) {
+fn validate_enum_attributes<I>(attrs: &I)
+where
+    for<'a> &'a I: IntoIterator<Item = &'a Attribute>,
+{
     // TODO: Later on we may want to enforce deriving clone and copy traits for all enum types
+    validate_attributes(attrs);
+}
+
+fn validate_attributes<I>(attrs: &I)
+where
+    for<'a> &'a I: IntoIterator<Item = &'a Attribute>,
+{
+    assert!(
+        !attrs.into_iter().any(|attr| attr.path().is_ident("repr")),
+        "using `repr` attribute is not allowed with `ast_node`."
+    );
 }
 
 fn impl_traversable_test_trait(node: &NodeData) -> TokenStream2 {