Raise exception so we don't run into this arg mismatch again

synapse/util/caches/descriptors.py

@@ -431,6 +431,12 @@ class DeferredCacheListDescriptor(_CacheDescriptorBase):
         cache: DeferredCache[CacheKey, Any] = cached_method.cache
         num_args = cached_method.num_args
 
+        if num_args != self.num_args:
+            raise Exception(
+                "Number of args (%s) does not match underlying cache_method_name=%s (%s)."
+                % (self.num_args, self.cached_method_name, num_args)
+            )
+
         @functools.wraps(self.orig)
         def wrapped(*args: Any, **kwargs: Any) -> "defer.Deferred[Dict]":
             # If we're passed a cache_context then we'll want to call its