diff --git a/scripts-dev/mypy_synapse_plugin.py b/scripts-dev/mypy_synapse_plugin.py
index 877b831751..509047b41b 100644
--- a/scripts-dev/mypy_synapse_plugin.py
+++ b/scripts-dev/mypy_synapse_plugin.py
@@ -38,6 +38,7 @@ from mypy.types import (
NoneType,
TupleType,
TypeAliasType,
+ TypeVarType,
UninhabitedType,
UnionType,
)
@@ -233,6 +234,7 @@ IMMUTABLE_CUSTOM_TYPES = {
"synapse.synapse_rust.push.FilteredPushRules",
# This is technically not immutable, but close enough.
"signedjson.types.VerifyKey",
+ "synapse.types.StrCollection",
}
# Immutable containers only if the values are also immutable.
@@ -298,7 +300,7 @@ def is_cacheable(
elif rt.type.fullname in MUTABLE_CONTAINER_TYPES:
# Mutable containers are mutable regardless of their underlying type.
- return False, None
+ return False, f"container {rt.type.fullname} is mutable"
elif "attrs" in rt.type.metadata:
# attrs classes are only cachable iff it is frozen (immutable itself)
@@ -318,6 +320,9 @@ def is_cacheable(
else:
return False, "non-frozen attrs class"
+ elif rt.type.is_enum:
+ # We assume Enum values are immutable
+ return True, None
else:
# Ensure we fail for unknown types, these generally means that the
# above code is not complete.
@@ -326,6 +331,18 @@ def is_cacheable(
f"Don't know how to handle {rt.type.fullname} return type instance",
)
+ elif isinstance(rt, TypeVarType):
+ # We consider TypeVars immutable if they are bound to a set of immutable
+ # types.
+ if rt.values:
+ for value in rt.values:
+ ok, note = is_cacheable(value, signature, verbose)
+ if not ok:
+ return False, f"TypeVar bound not cacheable {value}"
+ return True, None
+
+ return False, "TypeVar is unbound"
+
elif isinstance(rt, NoneType):
# None is cachable.
return True, None
|
