def generic_type_arguments_are_covariant():
type_bindings = {"f": types.generic_func(["T"], lambda T:
types.func([T, T], T),
)}
node = nodes.call(nodes.ref("f"), [nodes.str_literal(""), nodes.none()])
assert_equal(
types.common_super_type([types.str_type, types.none_type]),
infer(node, type_bindings=type_bindings)
)
def error_if_generic_func_is_passed_wrong_arguments():
type_bindings = {"f": types.generic_func(["T"], lambda T:
types.func([T, types.int_type], T),
)}
node = nodes.call(nodes.ref("f"), [nodes.str_literal(""), nodes.none()])
try:
infer(node, type_bindings=type_bindings)
assert False, "Expected error"
except errors.ArgumentsError as error:
assert_is(node, error.node)
assert_equal("cannot call function of type: T => T, int -> T\nwith arguments: str, NoneType", str(error))
def callee_can_be_generic_func():
type_bindings = {"f": types.generic_func(["T"], lambda T:
types.func([T], types.int_type),
)}
node = nodes.call(nodes.ref("f"), [nodes.str_literal("")])
assert_equal(types.int_type, infer(node, type_bindings=type_bindings))
