rig enum PyClass to be frozen

Author: mkovaxx

pyo3-macros-backend/src/pyclass.rs

@@ -777,9 +777,12 @@ fn impl_complex_enum(
     doc: PythonDoc,
     methods_type: PyClassMethodsType,
 ) -> Result<TokenStream> {
-    // Need to rig the enum PyClass to be subclassable by the variant PyClasses
+    // Need to rig the enum PyClass options
     let args = {
         let mut rigged_args = args.clone();
+        // Needs to be frozen to disallow `&mut self` methods, which could break a runtime invariant
+        rigged_args.options.frozen = parse_quote!(frozen);
+        // Needs to be subclassable by the variant PyClasses
         rigged_args.options.subclass = parse_quote!(subclass);
         rigged_args
     };
@@ -855,14 +858,10 @@ fn impl_complex_enum(
         };
         variant_cls_zsts.push(variant_cls_zst);
 
-        // TODO(mkovaxx): propagate variant.options
-        let options: PyClassPyO3Options = parse_quote! {
-            extends = #cls, frozen
-        };
-
         let variant_args = PyClassArgs {
             class_kind: PyClassKind::Struct,
-            options,
+            // TODO(mkovaxx): propagate variant.options
+            options: parse_quote!(extends = #cls, frozen),
             deprecations: Deprecations::new(),
         };