chore: checkpoint before Python removal

vendor/darling/tests/enums_struct.rs

@@ -0,0 +1,15 @@
+#![allow(dead_code)]
+
+//! Test expansion of enums which have struct variants.
+
+use darling::FromMeta;
+#[derive(Debug, FromMeta)]
+#[darling(rename_all = "snake_case")]
+enum Message {
+    Hello { user: String, silent: bool },
+    Ping,
+    Goodbye { user: String },
+}
+
+#[test]
+fn expansion() {}