Enable `--warn-redundant-casts` option in mypy (#14671)

* Enable `--warn-redundant-casts` option in mypy

Doesn't do much but helps me sleep better at night.

* Changelog

* Fix name of the ignore

* Fix one more missed cast

Not sure why I didn't see this one locally, maybe I needed a poetry update

* Remove old comment

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

2 files changed, 3 insertions, 2 deletions

diff --git a/synapse/storage/database.py b/synapse/storage/database.py

index 55bcb90001..0b29e67b94 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -667,7 +667,8 @@ class DatabasePool:
                 )
         # also check variables referenced in func's closure
         if inspect.isfunction(func):
-            f = cast(types.FunctionType, func)
+            # Keep the cast for now---it helps PyCharm to understand what `func` is.
+            f = cast(types.FunctionType, func)  # type: ignore[redundant-cast]
             if f.__closure__:
                 for i, cell in enumerate(f.__closure__):
                     if inspect.isgenerator(cell.cell_contents):
diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py

index 719a517336..f9f562ea45 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -77,7 +77,7 @@ class PostgresEngine(
         # docs: The number is formed by converting the major, minor, and
         # revision numbers into two-decimal-digit numbers and appending them
         # together. For example, version 8.1.5 will be returned as 80105
-        self._version = cast(int, db_conn.server_version)
+        self._version = db_conn.server_version
         allow_unsafe_locale = self.config.get("allow_unsafe_locale", False)
 
         # Are we on a supported PostgreSQL version?