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[perf] Add PHPStan rule to catch ScopeFetcher::fetch() before a scope-free guard - #8584
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…ore a scope-free return-null guard
TomasVotruba
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October 10, 2026 09:15
TomasVotruba
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Adds
NoScopeFetchBeforeCheapGuardRuleunderutils/phpstan, registered inphpstan.neon, to catch the perf shape fixed across #8579 / #8580 / #8582 before it lands again.It flags a
refactor()method where$scope = ScopeFetcher::fetch($node);is immediately followed by anif (...) { return null; }guard whose condition does not reference$scope. Such a guard is cheap and scope-free, so it should run before the fetch - most nodes then bail out before any scope resolution.Scope: deliberately narrow and dataflow-free to stay reliable. It only looks at the statement right after the fetch, so it does not catch cheap checks hidden inside a
shouldSkip($node, $scope)call (that call references$scope). Keeps false positives at zero - a fullcomposer phpstanrun over the current tree reports no hits outside the rule test fixtures.Covered by
NoScopeFetchBeforeCheapGuardRuleTestwith one failing and one passing fixture.