Method test_invalid_registrations

Lib/test/test_functools.py:3288–3336

(self)

        )

    def test_invalid_registrations(self):
        msg_prefix = "Invalid first argument to `register()`: "
        msg_suffix = (
            ". Use either `@register(some_class)` or plain `@register` on an "
            "annotated function."
        )
        @functools.singledispatch
        def i(arg):
            return "base"
        with self.assertRaises(TypeError) as exc:
            @i.register(42)
            def _(arg):
                return "I annotated with a non-type"
        self.assertStartsWith(str(exc.exception), msg_prefix + "42")
        self.assertEndsWith(str(exc.exception), msg_suffix)
        with self.assertRaises(TypeError) as exc:
            @i.register
            def _(arg):
                return "I forgot to annotate"
        self.assertStartsWith(str(exc.exception), msg_prefix +
            "<function TestSingleDispatch.test_invalid_registrations.<locals>._"
        )
        self.assertEndsWith(str(exc.exception), msg_suffix)

        with self.assertRaises(TypeError) as exc:
            @i.register
            def _(arg: typing.Iterable[str]):
                # At runtime, dispatching on generics is impossible.
                # When registering implementations with singledispatch, avoid
                # types from `typing`. Instead, annotate with regular types
                # or ABCs.
                return "I annotated with a generic collection"
        self.assertStartsWith(str(exc.exception),
            "Invalid annotation for 'arg'."
        )
        self.assertEndsWith(str(exc.exception),
            'typing.Iterable[str] is not a class.'
        )

        with self.assertRaises(TypeError) as exc:
            @i.register
            def _(arg: typing.Union[int, typing.Iterable[str]]):
                return "Invalid Union"
        self.assertStartsWith(str(exc.exception),
            "Invalid annotation for 'arg'."
        )
        self.assertEndsWith(str(exc.exception),
            'int | typing.Iterable[str] not all arguments are classes.'
        )

    def test_invalid_positional_argument(self):
        @functools.singledispatch