Fix up some typechecking (#6150)

* type checking fixes

* changelog

5 files changed, 33 insertions, 8 deletions

diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index f1c46836b1..0d3bdd88ce 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -13,9 +13,11 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
 import collections
 import logging
 from contextlib import contextmanager
+from typing import Dict, Sequence, Set, Union
 
 from six.moves import range
 
@@ -213,7 +215,9 @@ class Linearizer(object):
         # the first element is the number of things executing, and
         # the second element is an OrderedDict, where the keys are deferreds for the
         # things blocked from executing.
-        self.key_to_defer = {}
+        self.key_to_defer = (
+            {}
+        )  # type: Dict[str, Sequence[Union[int, Dict[defer.Deferred, int]]]]
 
     def queue(self, key):
         # we avoid doing defer.inlineCallbacks here, so that cancellation works correctly.
@@ -340,10 +344,10 @@ class ReadWriteLock(object):
 
     def __init__(self):
         # Latest readers queued
-        self.key_to_current_readers = {}
+        self.key_to_current_readers = {}  # type: Dict[str, Set[defer.Deferred]]
 
         # Latest writer queued
-        self.key_to_current_writer = {}
+        self.key_to_current_writer = {}  # type: Dict[str, defer.Deferred]
 
     @defer.inlineCallbacks
     def read(self, key):
diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index b50e3503f0..43fd65d693 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -16,6 +16,7 @@
 
 import logging
 import os
+from typing import Dict
 
 import six
 from six.moves import intern
@@ -37,7 +38,7 @@ def get_cache_factor_for(cache_name):
 
 
 caches_by_name = {}
-collectors_by_name = {}
+collectors_by_name = {}  # type: Dict
 
 cache_size = Gauge("synapse_util_caches_cache:size", "", ["name"])
 cache_hits = Gauge("synapse_util_caches_cache:hits", "", ["name"])
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 43f66ec4be..5ac2530a6a 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -18,10 +18,12 @@ import inspect
 import logging
 import threading
 from collections import namedtuple
+from typing import Any, cast
 
 from six import itervalues
 
 from prometheus_client import Gauge
+from typing_extensions import Protocol
 
 from twisted.internet import defer
 
@@ -37,6 +39,18 @@ from . import register_cache
 logger = logging.getLogger(__name__)
 
 
+class _CachedFunction(Protocol):
+    invalidate = None  # type: Any
+    invalidate_all = None  # type: Any
+    invalidate_many = None  # type: Any
+    prefill = None  # type: Any
+    cache = None  # type: Any
+    num_args = None  # type: Any
+
+    def __name__(self):
+        ...
+
+
 cache_pending_metric = Gauge(
     "synapse_util_caches_cache_pending",
     "Number of lookups currently pending for this cache",
@@ -245,7 +259,9 @@ class Cache(object):
 
 
 class _CacheDescriptorBase(object):
-    def __init__(self, orig, num_args, inlineCallbacks, cache_context=False):
+    def __init__(
+        self, orig: _CachedFunction, num_args, inlineCallbacks, cache_context=False
+    ):
         self.orig = orig
 
         if inlineCallbacks:
@@ -404,7 +420,7 @@ class CacheDescriptor(_CacheDescriptorBase):
                 return tuple(get_cache_key_gen(args, kwargs))
 
         @functools.wraps(self.orig)
-        def wrapped(*args, **kwargs):
+        def _wrapped(*args, **kwargs):
             # If we're passed a cache_context then we'll want to call its invalidate()
             # whenever we are invalidated
             invalidate_callback = kwargs.pop("on_invalidate", None)
@@ -440,6 +456,8 @@ class CacheDescriptor(_CacheDescriptorBase):
 
             return make_deferred_yieldable(observer)
 
+        wrapped = cast(_CachedFunction, _wrapped)
+
         if self.num_args == 1:
             wrapped.invalidate = lambda key: cache.invalidate(key[0])
             wrapped.prefill = lambda key, val: cache.prefill(key[0], val)
diff --git a/synapse/util/caches/treecache.py b/synapse/util/caches/treecache.py
index 9a72218d85..2ea4e4e911 100644
--- a/synapse/util/caches/treecache.py
+++ b/synapse/util/caches/treecache.py
@@ -1,3 +1,5 @@
+from typing import Dict
+
 from six import itervalues
 
 SENTINEL = object()
@@ -12,7 +14,7 @@ class TreeCache(object):
 
     def __init__(self):
         self.size = 0
-        self.root = {}
+        self.root = {}  # type: Dict
 
     def __setitem__(self, key, value):
         return self.set(key, value)
diff --git a/synapse/util/module_loader.py b/synapse/util/module_loader.py
index 7ff7eb1e4d..2705cbe5f8 100644
--- a/synapse/util/module_loader.py
+++ b/synapse/util/module_loader.py
@@ -54,5 +54,5 @@ def load_python_module(location: str):
     if spec is None:
         raise Exception("Unable to load module at %s" % (location,))
     mod = importlib.util.module_from_spec(spec)
-    spec.loader.exec_module(mod)
+    spec.loader.exec_module(mod)  # type: ignore
     return mod