[red-knot] is_subtype_of fix for KnownInstance types
#14750
Merged
Conversation
This file contains 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
`KnownInstance::instance_fallback` may return instances of supertypes. For example, it returns an instance of `_SpecialForm` for `Literal`. This means it can't be used on the right-hand side of `is_subtype_of` relationships, because it might lead to false positives. I can lead to false negatives on the left hand side of `is_subtype_of`, but this is at least a known limitation. False negatives are fine for most applications, but false positives can lead to wrong results in intersection-simplification, for example.
sharkdp
requested review from
carljm,
MichaReiser and
AlexWaygood
as code owners
|
AlexWaygood
approved these changes
Dec 3, 2024
dcreager
added a commit
that referenced
this pull request
Dec 3, 2024
* main: [`ruff`] Extend unnecessary-regular-expression to non-literal strings (`RUF055`) (#14679) Minor followups to RUF052 (#14755) [red-knot] Property tests (#14178) [red-knot] `is_subtype_of` fix for `KnownInstance` types (#14750) Improve docs for flake8-use-pathlib rules (#14741) [`ruff`] Implemented `used-dummy-variable` (`RUF052`) (#14611) [red-knot] Simplify tuples containing `Never` (#14744) Possible fix for flaky file watching test (#14543) [`flake8-import-conventions`] Improve syntax check for aliases supplied in configuration for `unconventional-import-alias (ICN001)` (#14745) [red-knot] Deeper understanding of `LiteralString` (#14649) red-knot: support narrowing for bool(E) (#14668) [`refurb`] Handle non-finite decimals in `verbose-decimal-constructor (FURB157)` (#14596) [red-knot] Re-enable linter corpus tests (#14736)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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.
Summary
KnownInstance::instance_fallbackmay return instances of supertypes. For example, it returns an instance of_SpecialFormforLiteral. This means it can't be used on the right-hand side ofis_subtype_ofrelationships, because it might lead to false positives.I can lead to false negatives on the left hand side of
is_subtype_of, but this is at least a known limitation. False negatives are fine for most applications, but false positives can lead to wrong results in intersection-simplification, for example.closes #14731
Test Plan
Added regression test