Fix resolution of candidates with empty intersections#6520
Open
Kirill Rakhman (cypressious) wants to merge 4 commits into
Open
Fix resolution of candidates with empty intersections#6520Kirill Rakhman (cypressious) wants to merge 4 commits into
Kirill Rakhman (cypressious) wants to merge 4 commits into
Conversation
Kirill Rakhman (cypressious)
commented
Jul 3, 2026
Kirill Rakhman (cypressious)
commented
Contributor
- [Tests] Reproduce #KT-86740
- [FIR] Fix resolution of candidates with empty intersection warning
- [FE] Move OnlyForDefaultLanguageFeatureDisabled to core.language.version-settings
- [FE] Mark RESOLVED_NEED_PRESERVE_COMPATIBILITY with OnlyForDefaultLanguageFeatureDisabled
^RCA: The applicability of InferredEmptyIntersectionDiagnostic was previously always INAPPLICABLE. When a callable reference resolved to a candidate with only this diagnostic, it would be marked as unsuccesful and in FirCallResolver.resolveCallableReference an early return would happen before the call to containingCallCS.replaceContentWith(chosenCandidate.system.currentStorage()). As a result, constraints that were created during the resolution of the callable reference would be lost. This isn't usually a problem because the candidate is unsuccessful anyway and we would expect the code to be red (or a different candidate to be chosen). However, InferredEmptyIntersectionDiagnostic is only mapped to a warning when ForbidInferringTypeVariablesIntoEmptyIntersection is disabled (which it currently is). As a result, the code is wrongly green and the compiler (maybe?) crashes in the backend. The handling of constraint systems of callable references was changed in KT-73771 which made the bug observable. However, the real cause is b64cb67 when the logic was implemented to "downgrade" InferredEmptyIntersectionDiagnostic to warnings. As a fix, the applicability of InferredEmptyIntersectionDiagnostic is set to RESOLVED_LOW_PRIORITY when it only leads to a warning. The reason why RESOLVED_LOW_PRIORITY is used instead of RESOLVED is because this diagnostic previously affected overload selection, and we want to prevent a breaking change in the form of introduced OVERLOAD_RESOLUTION_AMBIGUITYs. If an empty intersection leads to an error is additionally determined by its EmptyIntersectionTypeKind. This logic, which is also used in NewConstraintSystemImpl, is extracted to a helper EmptyIntersectionTypeKind.isError to prevent drift. This fix leads to red->green changes when there are multiple candidates, one has only an empty intersection warning, and the rest is otherwise inapplicable. Previously NONE_APPLICABLE would be reported, after the fix the candidate with the empty intersection warning is chosen. (see kt52393.kt and kt52431.kt) Because of this, a LF targeted to 2.5 is introduced to toggle the fix. #KT-86740 Fixed
…ion-settings ... and allow providing more than one feature
…guageFeatureDisabled
Code Owners
|
Contributor
Author
|
/dry-run |
|
THIS IS A DRY RUN Quality gate is triggered at https://buildserver.labs.intellij.net/build/993138263 — use this link to get full insight. Quality gate was triggered with the following revisions:
Quality gate failed. See https://buildserver.labs.intellij.net/build/993138263 to get full insight. |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.