temp2

scripts-dev/mypy_synapse_plugin.py

@@ -103,9 +103,29 @@ def cached_function_method_attribute(ctx: AttributeContext) -> mypy.types.Type:
             ctx.default_attr_type.type.fullname
             == "synapse.util.caches.descriptors.CachedFunction"
         ):
+            if getattr(ctx.context, "name") == "did_forget":
+                breakpoint()
+
             # Unwrap the wrapped function.
-            return _unwrap_cached_decoratored_function(
-                ctx.default_attr_type.args[0], ctx.api
+            wrapped_signature = ctx.default_attr_type.args[0]
+            assert isinstance(wrapped_signature, CallableType)
+
+            # 1. Mark this as a bound function signature.
+            signature: CallableType = bind_self(wrapped_signature)
+
+            # 4. Ensure the return type is a Deferred.
+            ret_arg = _get_true_return_type(signature)
+
+            # This should be able to use api.named_generic_type, but that doesn't seem
+            # to find the correct symbol for anything more than 1 module deep.
+            #
+            # modules is not part of CheckerPluginInterface. The following is a combination
+            # of TypeChecker.named_generic_type and TypeChecker.lookup_typeinfo.
+            sym = ctx.api.modules["twisted.internet.defer"].names.get("Deferred")  # type: ignore[attr-defined]
+            ret_type = Instance(sym.node, [remove_instance_last_known_values(ret_arg)])
+
+            return ctx.default_attr_type.copy_modified(
+                args=[signature.copy_modified(ret_type=ret_type)]
             )
 
     return ctx.default_attr_type