def operands_of_sub_operation_must_support_sub():
type_bindings = {"x": types.none_type, "y": types.none_type}
subtraction = nodes.sub(nodes.ref("x"), nodes.ref("y"))
try:
infer(subtraction, type_bindings=type_bindings)
assert False, "Expected error"
except errors.NoSuchAttributeError as error:
assert_equal(nodes.attr(subtraction.left, "__sub__"), error.node)
def can_infer_type_of_subtraction_operation():
type_bindings = {"x": types.int_type, "y": types.int_type}
subtraction = nodes.sub(nodes.ref("x"), nodes.ref("y"))
assert_equal(types.int_type, infer(subtraction, type_bindings=type_bindings))
def test_parse_subtraction():
expected = nodes.sub(nodes.ref("x"), nodes.ref("y"))
_assert_expression_parse(expected, "x - y")