Fix phpstan/phpstan#14421: Incorrect type narrowing of superglobal with dependent types#5377
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phpstan-bot wants to merge 1 commit intophpstan:2.1.xfrom
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Fix phpstan/phpstan#14421: Incorrect type narrowing of superglobal with dependent types#5377phpstan-bot wants to merge 1 commit intophpstan:2.1.xfrom
phpstan-bot wants to merge 1 commit intophpstan:2.1.xfrom
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- Extended conditional expression skip logic in MutatingScope to handle superglobal variables not present in the other branch's expression types - Added exprContainsSuperGlobal() helper method to detect superglobal expressions for reuse across merge logic - New regression test in tests/PHPStan/Rules/Variables/data/bug-14421.php - Root cause: superglobals always exist but aren't tracked in expressionTypes unless narrowed, so the dependent type skip check failed to recognize them
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Summary
When using
isset()on a superglobal array offset (e.g.,$_SESSION['a']) with dependent type narrowing, PHPStan incorrectly reported that the offset always exists and is not nullable, even when the code path could bypass theisset()branch.Changes
src/Analyser/MutatingScope.phpto handle superglobal variables that aren't present in the other branch's expression typesexprContainsSuperGlobal()helper method to detect whether an expression involves a superglobal variabletests/PHPStan/Rules/Variables/data/bug-14421.phpand test method intests/PHPStan/Rules/Variables/IssetRuleTest.phpRoot cause
The fix for phpstan/phpstan#14411 added a check to skip creating conditional expressions when both the expression and its guard exist with certainty in the other branch. However, superglobal variables like
$_SESSIONare always defined but aren't tracked inexpressionTypesunless they've been narrowed by a type specification (e.g., fromisset()). When$_SESSIONwas narrowed in the if-branch but not present in the else-branch's expression types, the skip check failed, causing incorrect conditional expressions to be created. These conditional expressions then incorrectly linked$b's type to$_SESSION's narrowed type, so narrowing$b !== nullalso incorrectly narrowed$_SESSION.The fix treats superglobal expressions as always existing with certainty, even when not explicitly tracked in the other branch's expression types.
Test
Added a regression test reproducing the exact scenario from the issue:
isset($_SESSION['a'])with a fallback assignment in the else branch, followed by a null check that should not cause theisset()to be flagged as always true.Fixes phpstan/phpstan#14421