def instantiated_generic_structural_type_is_sub_type_of_other_instantiated_generic_structural_type_if_it_has_matching_attributes(self):
iterator = types.generic_structural_type("iterator", [types.covariant("T")], lambda T: [
types.attr("__iter__", types.func([], iterator(T))),
types.attr("__next__", types.func([], T)),
])
iterable = types.generic_structural_type("iterable", [types.covariant("T")], lambda T: [
types.attr("__iter__", types.func([], iterator(T))),
])
assert types.is_sub_type(
iterable(types.int_type),
iterator(types.int_type),
)
def recursive_instantiated_generic_structural_type_is_sub_type_of_same_instantiated_generic_structural_type_if_it_has_matching_attributes(self):
recursive = types.generic_structural_type("recursive", [types.covariant("T")], lambda T: [
types.attr("__iter__", types.func([], recursive(T))),
])
assert types.is_sub_type(
recursive(types.int_type),
recursive(types.int_type),
)
def invariant_type_parameter_can_be_unified_when_part_of_recursive_structural_type(self):
invariant_type_param = types.invariant("T")
recursive = types.generic_structural_type("recursive", [types.covariant("T")], lambda T: [
types.attr("__iter__", types.func([], recursive(T))),
])
assert types.is_sub_type(
recursive(invariant_type_param),
recursive(types.int_type),
unify=[invariant_type_param]
)
def covariant_type_parameter_is_substituted_with_common_super_type_of_actual_type_params(self):
covariant_type_param = types.covariant("T")
first_class_type = types.class_type("User")
second_class_type = types.class_type("Role")
generic_class = types.generic_class("Pair", [covariant_type_param, covariant_type_param])
type_map = types.is_sub_type(
# TODO: need a reliable way of getting the underlying type (but as an instantiated type)
generic_class(covariant_type_param, covariant_type_param),
generic_class(first_class_type, second_class_type),
unify=[covariant_type_param]
)
assert_equal(types.union(first_class_type, second_class_type), type_map[covariant_type_param])
def instantiated_class_is_sub_type_of_other_instantiated_class_if_formal_param_is_covariant_and_type_params_are_subtypes(self):
generic_class = types.generic_class("iterator", [types.covariant("T")])
assert types.is_sub_type(generic_class(types.object_type), generic_class(types.int_type))
assert not types.is_sub_type(generic_class(types.int_type), generic_class(types.object_type))