Review comments.

synapse/http/client.py

@@ -78,7 +78,7 @@
 from synapse.http.types import QueryParams
 from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.logging.opentracing import set_tag, start_active_span, tags
-from synapse.types import BytesSequence, ISynapseReactor, StrSequence
+from synapse.types import ISynapseReactor, StrSequence
 from synapse.util import json_decoder
 from synapse.util.async_helpers import timeout_deferred
 
@@ -108,9 +108,10 @@
 # the value actually has to be a List, but List is invariant so we can't specify that
 # the entries can either be Lists or bytes.
 RawHeaderValue = Union[
-    BytesSequence,
     StrSequence,
+    List[bytes],
     List[Union[str, bytes]],
+    Tuple[bytes, ...],
     Tuple[Union[str, bytes], ...],
 ]
 

synapse/storage/databases/main/event_federation.py

@@ -47,7 +47,7 @@
 from synapse.storage.databases.main.events_worker import EventsWorkerStore
 from synapse.storage.databases.main.signatures import SignatureWorkerStore
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
-from synapse.types import JsonDict, StrCollection
+from synapse.types import JsonDict, StrCollection, StrSequence
 from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
 from synapse.util.caches.lrucache import LruCache
@@ -1179,7 +1179,7 @@ def _get_rooms_with_many_extremities_txn(txn: LoggingTransaction) -> List[str]:
         )
 
     @cached(max_entries=5000, iterable=True)
-    async def get_latest_event_ids_in_room(self, room_id: str) -> List[str]:
+    async def get_latest_event_ids_in_room(self, room_id: str) -> StrSequence:
         return await self.db_pool.simple_select_onecol(
             table="event_forward_extremities",
             keyvalues={"room_id": room_id},

synapse/types/__init__.py

@@ -95,7 +95,6 @@
 #
 # Unlike StrCollection, StrSequence is an ordered collection of strings.
 StrSequence = Union[Tuple[str, ...], List[str]]
-BytesSequence = Union[Tuple[bytes, ...], List[bytes]]
 
 
 # Note that this seems to require inheriting *directly* from Interface in order