Do not let conditional expression undo explicit type narrowing#5710
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ondrejmirtes merged 1 commit intoMay 19, 2026
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When filterBySpecifiedTypes processes a condition like `$this->b !== null`, it narrows the expression and then resolves conditional expression holders. A CE chain could derive `$this->a = null` (from mutual exclusion) and then use that to trigger a "remove $this->b from scope" CE, undoing the explicit narrowing. This fix skips certainty-No CEs for expressions that were already narrowed by the original type specifications. Closes phpstan/phpstan#14645
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Summary
if (A && B) throwleaked narrowing across laterif (B !== null)checks, causing "Cannot call method on X|null" false positivefilterBySpecifiedTypes, skip conditional expression holders with certaintyNo(remove from scope) when the target expression was already explicitly narrowed by the current type specificationsRoot cause
When processing
if ($this->b !== null):$this->bis narrowed to non-null (from the condition)$this->bis non-null, then$this->ais null" (from earlier mutual exclusion)$this->ais null, remove$this->bfrom scope" — this undoes the narrowing from step 1Step 3 contradicts the explicit condition. The fix prevents "remove from scope" CEs from overriding expressions that were directly narrowed by the current type specification.
Test plan
tests/PHPStan/Analyser/nsrt/bug-14645.phpfails without fix, passes with fixmake tests— all 12121 tests passmake phpstan— no errorsmake cs-fix— no violationsCloses phpstan/phpstan#14645