Literal infers tuple literal as Union of the items though this syntax is forbidden by PEP 586

The section Illegal parameters for Literal at type check time describes that tuple literals inside Literal are forbidden:

Tuples containing valid literal types like Literal[(1, "foo", "bar")]. The user could always express this type as Tuple[Literal[1], Literal["foo"], Literal["bar"]] instead. Also, tuples are likely to be confused with the Literal[1, 2, 3] shortcut.

Nevertheless mypy seems to be taking this shortcut since it doesn't flag the following code:

from typing_extensions import Literal

a : Literal[(1, 2)] = 1 

Python 3.7, mypy 0.740, typing-extensions 3.7.4.

Empieza reproduciendo el fragmento de Python indicado con Literal[(1, 2)] y confirma si mypy lo acepta. Localiza la ruta de comprobación de tipos de Literal y sus pruebas existentes; se considera terminado cuando los literales de tupla en Literal se rechazan de acuerdo con PEP 586.