Add some type hints to datastore (#12485)

synapse/storage/databases/main/__init__.py

@@ -15,12 +15,17 @@
 # limitations under the License.
 
 import logging
-from typing import TYPE_CHECKING, List, Optional, Tuple
+from typing import TYPE_CHECKING, List, Optional, Tuple, cast
 
 from synapse.config.homeserver import HomeServerConfig
-from synapse.storage.database import DatabasePool, LoggingDatabaseConnection
+from synapse.storage.database import (
+    DatabasePool,
+    LoggingDatabaseConnection,
+    LoggingTransaction,
+)
 from synapse.storage.databases.main.stats import UserSortOrder
-from synapse.storage.engines import PostgresEngine
+from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine
+from synapse.storage.types import Cursor
 from synapse.storage.util.id_generators import (
     IdGenerator,
     MultiWriterIdGenerator,
@@ -266,7 +271,9 @@ class DataStore(
             A tuple of a list of mappings from user to information and a count of total users.
         """
 
-        def get_users_paginate_txn(txn):
+        def get_users_paginate_txn(
+            txn: LoggingTransaction,
+        ) -> Tuple[List[JsonDict], int]:
             filters = []
             args = [self.hs.config.server.server_name]
 
@@ -301,7 +308,7 @@ class DataStore(
                 """
             sql = "SELECT COUNT(*) as total_users " + sql_base
             txn.execute(sql, args)
-            count = txn.fetchone()[0]
+            count = cast(Tuple[int], txn.fetchone())[0]
 
             sql = f"""
                 SELECT name, user_type, is_guest, admin, deactivated, shadow_banned,
@@ -338,7 +345,9 @@ class DataStore(
         )
 
 
-def check_database_before_upgrade(cur, database_engine, config: HomeServerConfig):
+def check_database_before_upgrade(
+    cur: Cursor, database_engine: BaseDatabaseEngine, config: HomeServerConfig
+) -> None:
     """Called before upgrading an existing database to check that it is broadly sane
     compared with the configuration.
     """