from typing import TypeAliasType
import weakref
import gc
class S(str):
    pass
def still_alive(ref):
    obj = ref()
    if not isinstance(obj, S):
        return False
    T = obj.T
    if not isinstance(T, TypeAliasType):
        return False
    return T
name = S("name")
T = TypeAliasType(name, int)
name.T = T
ref = weakref.ref(name)
assert still_alive(ref)
del name
del T
gc.collect()
gc.collect()
assert still_alive(ref)
del ref().T
assert not still_alive(ref)