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.

Beginne damit, das gemeldete Python-Snippet mit Literal[(1, 2)] zu reproduzieren, und bestätige, ob mypy es akzeptiert. Finde den Pfad für die Literal-Typprüfung und die vorhandenen Tests dazu; als erledigt gilt die Aufgabe, wenn Tupel-Literale in Literal gemäß PEP 586 abgelehnt werden.