Feature request: `typing.Literal`

[redsun82]

Could we have PEP586 implemented in the type extension? I think that would be handy in a configuration language. There's enum, but that requires using the enum constructor. For me it would be nice to express that a certain argument expects something from a set of specific values, especially strings.

[ndmitchell]

We don't currently have any plans to refine the type system to follow the latest Python type specification.