Suppress false positives from mypy

synapse/storage/database.py

@@ -1684,7 +1684,11 @@ class DatabasePool:
             table,
             keyvalues,
             retcol,
-            allow_none=allow_none,
+            # Type ignore suppresses a mypy bug:
+            #     Argument "allow_none" to "runInteraction_advanced" of "DatabasePool"
+            #     has incompatible type "bool"; expected "Literal[False]"  [arg-type]
+            # I think mypy is confused by the overloads of simple_select_one_onecol_txn.
+            allow_none=allow_none,  # type:ignore[arg-type]
         )
 
     @overload

synapse/storage/databases/state/store.py

@@ -547,6 +547,9 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
             return state_group
 
         if prev_group is not None:
+            # This assertion is for mypy's benefit and is checked above.
+            assert delta_ids is not None
+
             state_group = await self.db_pool.runInteraction(
                 "store_state_group.insert_delta_group",
                 insert_delta_group_txn,