Error when importing Enum from different file

[twoertwein]

Describe the bug
Pyright does not report errors, when declaring the enum within the same file where it is being used. When importing the same enum from a different file, pyright reports an error.

To Reproduce

bar.py

from enum import Enum
from typing import Literal

# similar to https://github.com/python/typeshed/pull/7127/files
class _NoDefault(Enum):
    no_default = "NO_DEFAULT"

no_default = _NoDefault.no_default  # Sentinel indicating the default value.
NoDefault = Literal[_NoDefault.no_default]

def test(x: NoDefault = no_default):
    ...

pyright reports no errors for bar.py

foo.py

import bar

reveal_type(bar.NoDefault)
reveal_type(bar.no_default)

def test(x: bar.NoDefault = bar.no_default):
    ...

pyright reports:
3:13 - information: Type of "bar.NoDefault" is "Type[Literal[_NoDefault.no_default]]"
4:13 - information: Type of "bar.no_default" is "_NoDefault"
6:29 - error: Expression of type "_NoDefault" cannot be assigned to parameter of type "NoDefault"

Expected behavior
It seems that pyright has troubles inferring bar.no_default, it should be bar._NoDefault.no_default and not bar._NoDefault.

[twoertwein]

Changing the lines in bar to.py

NoDefault = Literal[_NoDefault.no_default]
no_default: NoDefault = _NoDefault.no_default  # Sentinel indicating the default value.

avoids this issue.

[erictraut]

Yes, this behavior is intended. The variable no_default has no type annotation, so its type is inferred. In this case, it has an inferred type of _NoDefault. Locally, its type is narrowed to the type Literal[_NoDefault.no_default] because of the assignment. When you import that variable from another module, the local type narrowing is not applied, so its type is simply NoDefault. If your intent is for no_default to have the type Literal[_NoDefault.no_default], you should annotate it as such.

Even better, if your intent is for this variable to be constant, you should annotate it as Final. When inferring the type of a Final variable, pyright retains the literal type.

no_default: Final = _NoDefault.no_default