Audit public API and SemVer surface (#103)

tools/generate_rust_mapping.py

@@ -1271,7 +1271,19 @@ def parameter_slug(value: str) -> str:
 def member_signature(mapper: Mapper, owner: dict, item: dict, rust_name: str) -> tuple[str, str, str, str, str]:
     if item["doc_id"] in MEMBER_SIGNATURE_OVERRIDES:
         signature, ownership = MEMBER_SIGNATURE_OVERRIDES[item["doc_id"]]
-        return signature, ownership, "sync", "Result<_, crate::Error>", "method"
+        error_model = (
+            "none"
+            if item["doc_id"] == "P:LibreMetaverse.ExpiringCache`2.Item(`0)"
+            else "Result<_, crate::Error>"
+        )
+        asyncness = (
+            "async"
+            if signature.startswith("pub async fn")
+            else "boxed_future"
+            if "dyn std::future::Future" in signature
+            else "sync"
+        )
+        return signature, ownership, asyncness, error_model, "method"
     generics = generic_names(item, owner)
     mapped_parameters = [map_parameter(mapper, parameter, generics) for parameter in item.get("parameters", [])]
     packet_owner = owner["doc_id"].startswith("T:LibreMetaverse.Packets.")