Fix #12250: False positive Property HelloWorld::$bug (WeakMap<stdClass, stdClass>) does not accept WeakMap<object, mixed>|WeakMap<stdClass, stdClass>.#4958
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- Added handling for AssignOp\Coalesce in NewAssignedToPropertyVisitor - The visitor now marks `new` expressions in `$this->prop ??= new Foo()` with the property attribute, so MutatingScope::exactInstantiation() can infer generic type parameters from the property's declared type - New regression test in tests/PHPStan/Rules/Properties/data/bug-12250.php Closes phpstan/phpstan#12250
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Summary
When a generic class like
WeakMapis instantiated and assigned to a typed property using the null coalesce assignment operator (??=), PHPStan failed to infer the generic type parameters from the property's declared type. This caused a false positive like:Changes
src/Parser/NewAssignedToPropertyVisitor.phpto also handleNode\Expr\AssignOp\Coalescein addition toAssignandAssignReftests/PHPStan/Rules/Properties/data/bug-12250.phptestBug12250()intests/PHPStan/Rules/Properties/TypesAssignedToPropertiesRuleTest.phpRoot cause
NewAssignedToPropertyVisitoris a parser visitor that marksnewexpressions assigned to properties with an attribute, so thatMutatingScope::exactInstantiation()can later infer generic type parameters from the property's declared type. The visitor handledAssign(=) andAssignRef(=&), but notAssignOp\Coalesce(??=). Without the attribute,new WeakMap()in$this->bug ??= new WeakMap()was typed asWeakMap<object, mixed>(the default generic bounds) instead ofWeakMap<stdClass, stdClass>(from the property declaration).Test
The regression test verifies that
$this->bug ??= new WeakMap()produces no errors when the property is typed asWeakMap<stdClass, stdClass>, alongside a regular assignment$this->ok = new WeakMap()that already worked correctly.Fixes phpstan/phpstan#12250
Closes phpstan/phpstan#4525