Make it possible to use dmypy (#9692)

Running `dmypy run` will do a `mypy` check while spinning up a daemon
that makes rerunning `dmypy run` a lot faster.

`dmypy` doesn't support `follow_imports = silent` and has
`local_partial_types` enabled, so this PR enables those options and
fixes the issues that were newly raised. Note that `local_partial_types`
will be enabled by default in upcoming mypy releases.

1 files changed, 2 insertions, 2 deletions

diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py

index f968706334..48f64eeb38 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -25,8 +25,8 @@ from synapse.config.cache import add_resizable_cache
 
 logger = logging.getLogger(__name__)
 
-caches_by_name = {}
-collectors_by_name = {}  # type: Dict
+caches_by_name = {}  # type: Dict[str, Sized]
+collectors_by_name = {}  # type: Dict[str, CacheMetric]
 
 cache_size = Gauge("synapse_util_caches_cache:size", "", ["name"])
 cache_hits = Gauge("synapse_util_caches_cache:hits", "", ["name"])