Enum type not assignable to complete union of its literal members

[ericmarkmartin]

Describe the bug
According to the typing spec for enums,

a type checker should treat a complete union of all literal members as equivalent to the enum type, but not from the enum type to the union.

However, Pyright currently only allows assignment from the union to the enum type, but not from the enum type to the union.

Code or Screenshots

from enum import Enum
from typing import Literal

class Color(Enum):
    RED = "red"
    GREEN = "green"
    BLUE = "blue"

def contraction_id(c: Literal[Color.RED, Color.GREEN, Color.BLUE]) -> Color:
    return c

def expansion_id(c: Color) -> Literal[Color.RED, Color.GREEN, Color.BLUE]:
    return c

The error reported is

Type "Color" is not assignable to return type "Literal[Color.RED, Color.GREEN, Color.BLUE]"
  Type "Color" is not assignable to type "Literal[Color.RED, Color.GREEN, Color.BLUE]"
    "Color" is not assignable to type "Literal[Color.RED]"
    "Color" is not assignable to type "Literal[Color.GREEN]"
    "Color" is not assignable to type "Literal[Color.BLUE]"  (reportReturnType)

VS Code extension or command-line

Pyright playground

[erictraut]

Your sample has syntax errors in it. Here's a corrected snippet:

from enum import Enum
from typing import Literal

class Color(Enum):
    RED = "red"
    GREEN = "green"
    BLUE = "blue"

def contraction_id(c: Literal[Color.RED, Color.GREEN, Color.BLUE]) -> Color:
    return c

def expansion_id(c: Color) -> Literal[Color.RED, Color.GREEN, Color.BLUE]:
    return c

[ericmarkmartin]

Your sample has syntax errors in it.

Apologies, I was inputting this from my phone since I didn't have a personal machine accessible. I'll update my snippet to yours