NotificationsYou must be signed in to change notification settings
Fork3.1k
Star20.1k

prevent false unreachable warnings for @final instances that occur when strict optional checking is disabled#20045

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to ourterms of service andprivacy statement. We’ll occasionally send you account related emails.

Already on GitHub?Sign in to your account

Jump to bottom

Merged

ilevkivskyi merged 2 commits intopython:masterfromtyralla:fix/unreachable_nostrictoptional_final

Oct 12, 2025

Merged

prevent false unreachable warnings for @final instances that occur when strict optional checking is disabled#20045

ilevkivskyi merged 2 commits intopython:masterfromtyralla:fix/unreachable_nostrictoptional_final

Oct 12, 2025

Conversation

Copy link

Collaborator

tyralla commentedOct 10, 2025

Fixes#19849

See#11717 for some background information on--no-strict-optional.

Prevent false unreachable warnings for@Finalinstances that occur wh…

55fb9a6

…en strict optional checking is disabled.

This comment has been minimized.

sterliakov approved these changes

Oct 10, 2025

View reviewed changes

Copy link

Collaborator

sterliakov left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others.Learn more.

Primer change looks correct to me,result is defined earlier at L470 to an incompatible type. This branch was apparently unreachable before this change.

Copy link

CollaboratorAuthor

Yes, I think you are right. Mypy thought the branch was unreachable becauseEQUAL_NULL_PATTERN.match(constraint) returnsMatch | None, which it interprets asMatch because of--no-strict-optional.

@ilevkivskyi: Not a super critical bug, but at least a super simple fix. Could you take a look at it?

tyralla requested a review fromilevkivskyi

October 11, 2025 08:53

ilevkivskyi reviewed

Oct 11, 2025

View reviewed changes

mypy/typeops.py

		returnUninhabitedType(line=t.line)
		elifisinstance(t,Instance):
		ift.type.is_finalort.type.is_enum:
		if(t.type.is_finalort.type.is_enum)andstate.strict_optional:

Copy link

Member

ilevkivskyiOct 11, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others.Learn more.

I think this should apply to the branch just below as well. I mean what if in your test you will havex: Optional[Literal[SomeEnum.Foo]]? Or those are not simplified when strict optional isFalse?

Copy link

CollaboratorAuthor

tyrallaOct 11, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others.Learn more.

Thanks, you're right. I did as suggested and added the corresponding test casetestNoWrongUnreachableWarningWithNoStrictOptionalAndEnumLiteral.

Do the same for enum literals.

13af01b

Copy link

Contributor

github-actionsbot commentedOct 11, 2025

Diff frommypy_primer, showing the effect of this PR on open source code:

pwndbg (https://github.com/pwndbg/pwndbg)+ pwndbg/aglib/onegadget.py: note: In function "check_constraint":+ pwndbg/aglib/onegadget.py:495: error: Argument 1 to "find" has incompatible type "CheckSatResult"; expected "int | Value | None"  [arg-type]+ pwndbg/aglib/onegadget.py:507: error: Argument 1 to "find" has incompatible type "CheckSatResult"; expected "int | Value | None"  [arg-type]