Fix #13023: function.alreadyNarrowedType and function.impossibleType after updates to 2.1.15#5084
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- In ImpossibleCheckTypeHelper::findSpecifiedType(), treat class-specific type checks on $this as uncertain when inside a trait, since $this is polymorphic across the different classes that use the trait - Added isThis() helper method for detecting $this expression references - New regression test in tests/PHPStan/Rules/Comparison/data/bug-13023.php Closes phpstan/phpstan#13023
| $argumentType = $scope->getType($assignedInCallVar->expr); | ||
| } | ||
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| if ($isInTrait && self::isThis($sureType[0]) && $resultType->getObjectClassNames() !== []) { |
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Could be great to handle https://phpstan.org/r/73b2d6e1-9661-4375-b01d-cdd6ec39c69e too.
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Summary
When a trait method contains
is_a($this, SomeClass::class)and the trait is used by multiple classes, PHPStan falsely reports:function.alreadyNarrowedType("will always evaluate to true") when analyzing the trait in the context ofSomeClassfunction.impossibleType("will always evaluate to false") when analyzing the trait in the context ofSomeClass2Both are false positives because the trait code is shared across classes and the check is valid polymorphic behavior.
Changes
src/Rules/Comparison/ImpossibleCheckTypeHelper.php:findSpecifiedType(), added checks in both thesureTypesandsureNotTypesloops to treat class-specific type checks on$thisas uncertain (TrinaryLogic::createMaybe()) when the scope is inside a traitisThis()private static helper to detect$thisvariable expressionstests/PHPStan/Rules/Comparison/data/bug-13023.phptestBug13023()inImpossibleCheckTypeFunctionCallRuleTest.phpRoot cause
PHPStan analyzes trait methods once per class that uses the trait, each time with
$thistyped as that specific class. TheImpossibleCheckTypeHelper::findSpecifiedType()method compares the narrowed type (e.g.,ObjectType('SomeClass')) against the argument type (e.g.,$this(SomeClass)or$this(SomeClass2)), producing a definitive yes/no result for each class context. However, since trait code is shared, these definitive results are false positives.The fix detects when we're in a trait context and the sure type expression is
$thiswith a class-specific result type (i.e.,getObjectClassNames() !== []). In that case, the result is treated as uncertain, preventing the false positive. Non-class-specific checks likeis_int($this)oris_object($this)are not affected, as they produce correct results regardless of which class uses the trait.Test
Added
tests/PHPStan/Rules/Comparison/data/bug-13023.phpwith a traitMyTraitused bySomeClassandSomeClass2, where the trait method callsis_a($this, SomeClass::class). The test expects no errors (empty array), confirming the false positives are suppressed.Fixes phpstan/phpstan#13023