Fix narrowing to non-falsy-string when '' and '0' equality checks are in compound conditions#5688
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When checking '' and '0' in a single || or && expression, the type narrowing to non-falsy-string was lost because the sequential removal of constant string types from the scope was lossy — removing '0' from 'string' cannot be represented, so the removal information was lost before '' could be removed (which would have enabled the '0' removal to succeed on the narrower non-empty-string type). Two fixes: 1. TypeCombinator::remove() now retries union type member removals in a loop, so that removing ''|'0' from string correctly yields non-falsy-string regardless of member ordering. 2. BooleanAndHandler/BooleanOrHandler now re-apply "lossy" sureNotType removals from the left arm after the right arm's narrowing succeeds, enabling the sequential per-arm path to also produce non-falsy-string. Closes phpstan/phpstan#9114
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Summary
Fixes phpstan/phpstan#9114
When
''and'0'equality checks appear in a compound boolean condition (||or&&), PHPStan failed to narrow the variable tonon-falsy-string. This happened because removing'0'fromstringis "lossy" (cannot be represented in the type system), so by the time''removal narrowed the type tonon-empty-string, the'0'removal information was already lost.Changes
TypeCombinator::remove(): When removing a union type, retry members that failed in a loop until no more progress is made. This handles the case where removing''|'0'fromstringnow correctly producesnon-falsy-stringregardless of member ordering.BooleanAndHandler: After computing the truthy scope, re-apply left arm's sureNotType removals that were previously lossy but can now succeed on the narrower type from the right arm.BooleanOrHandler: Same logic for the falsey scope computation.Test cases
All variants from the issue are covered:
'' === $foo || '0' === $foofollowed by throw →non-falsy-string'0' === $foo || '' === $foofollowed by throw →non-falsy-string'' !== $foo && '0' !== $foo→non-falsy-stringin truthy branch'0' !== $foo && '' !== $foo→non-falsy-stringin truthy branchTest plan
tests/PHPStan/Analyser/nsrt/bug-9114.phppassesmake phpstanself-analysis passes with no errors