gnutix · Jul 2, 2026
diff --git a/src/Rules/Properties/AccessStaticPropertiesCheck.php b/src/Rules/Properties/AccessStaticPropertiesCheck.php
@@ -16,6 +16,7 @@
 use PHPStan\DependencyInjection\AutowiredParameter;
 use PHPStan\DependencyInjection\AutowiredService;
 use PHPStan\Internal\SprintfHelper;
+use PHPStan\Node\Expr\TypeExpr;
 use PHPStan\Php\PhpVersion;
 use PHPStan\Reflection\ReflectionProvider;
 use PHPStan\Rules\ClassNameCheck;
@@ -175,9 +176,21 @@ private function processSingleProperty(Scope $scope, StaticPropertyFetch $node,
 				$classType = $scope->resolveTypeByName($node->class);
 			}
 		} else {
+			$exprToCheck = NullsafeOperatorHelper::getNullsafeShortcircuitedExprRespectingScope($scope, $node->class);
+			// A constant class-name string or a class-string type describes the
+			// object it names, so route the check through that object type. This
+			// makes constant-string / class-string unions behave exactly like
+			// object unions with regard to rule levels (member filtering when
+			// checkUnionTypes is off, whole-union check when it is on).
+			// Every other type (objects, or unions with members that are not
+			// class-strings) yields no class name here and keeps the old path.
+			$objectType = $scope->getType($exprToCheck)->getClassStringObjectType();
+			if ($this->canCheckThroughObjectType($objectType)) {
+				$exprToCheck = new TypeExpr($objectType);
+			}
 			$classTypeResult = $this->ruleLevelHelper->findTypeToCheck(
 				$scope,
-				NullsafeOperatorHelper::getNullsafeShortcircuitedExprRespectingScope($scope, $node->class),
+				$exprToCheck,
 				sprintf('Access to static property $%s on an unknown class %%s.', SprintfHelper::escapeFormatString($name)),
 				static fn (Type $type): bool => $type->canAccessProperties()->yes() && $type->hasStaticProperty($name)->yes(),
 			);
@@ -339,4 +352,25 @@ private function processSingleProperty(Scope $scope, StaticPropertyFetch $node,
 		]);
 	}
 
+	/**
+	 * Class-strings without a class name (class-string, class-string<object>,
+	 * class-string<T of object>) and class-strings naming a trait keep the
+	 * string code path: RuleLevelHelper would filter the object type out or
+	 * report the trait as an unknown class.
+	 */
+	private function canCheckThroughObjectType(Type $objectType): bool
+	{
+		if (count($objectType->getObjectClassNames()) === 0) {
+			return false;
+		}
+
+		foreach ($objectType->getObjectClassReflections() as $classReflection) {
+			if ($classReflection->isTrait()) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Properties/AccessStaticPropertiesInAssignRuleTest.php b/tests/PHPStan/Rules/Properties/AccessStaticPropertiesInAssignRuleTest.php
@@ -109,4 +109,46 @@ public function testAsymmetricVisibility(): void
 		]);
 	}
 
+	#[RequiresPhp('>= 8.0.0')]
+	public function testWritesOnStringUnions(): void
+	{
+		$this->analyse([__DIR__ . '/data/static-property-string-unions-assign.php'], [
+			[
+				'Access to an undefined static property StaticPropertyStringUnionsAssign\Baz::$missing.',
+				32,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnionsAssign\Baz::$missing.',
+				38,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnionsAssign\Baz::$missing.',
+				44,
+			],
+			[
+				'Access to private property $secret of class StaticPropertyStringUnionsAssign\Foo.',
+				50,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnionsAssign\Baz|StaticPropertyStringUnionsAssign\Foo::$count.',
+				56,
+			],
+		]);
+	}
+
+	#[RequiresPhp('>= 8.5.0')]
+	public function testAsymmetricVisibilityOnConstantString(): void
+	{
+		$this->analyse([__DIR__ . '/data/static-property-string-unions-asymmetric.php'], [
+			[
+				'Access to private(set) property $privateSet of class StaticPropertyStringUnionsAsymmetric\Foo.',
+				16,
+			],
+			[
+				'Access to protected(set) property $protectedSet of class StaticPropertyStringUnionsAsymmetric\Foo.',
+				17,
+			],
+		]);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Properties/AccessStaticPropertiesRuleTest.php b/tests/PHPStan/Rules/Properties/AccessStaticPropertiesRuleTest.php
@@ -21,14 +21,16 @@
 class AccessStaticPropertiesRuleTest extends RuleTestCase
 {
 
+	private bool $checkUnionTypes = true;
+
 	protected function getRule(): Rule
 	{
 		$reflectionProvider = self::createReflectionProvider();
 		$ruleLevelHelper = new RuleLevelHelper(
 			$reflectionProvider,
 			checkNullables: true,
 			checkThisOnly: false,
-			checkUnionTypes: true,
+			checkUnionTypes: $this->checkUnionTypes,
 			checkExplicitMixed: false,
 			checkImplicitMixed: false,
 			checkBenevolentUnionTypes: false,
@@ -396,4 +398,95 @@ public function testBug15002(): void
 		$this->analyse([__DIR__ . '/../Methods/data/bug-15002.php'], []);
 	}
 
+	#[RequiresPhp('>= 8.0.0')]
+	public function testStaticPropertyAccessOnStringUnions(): void
+	{
+		$this->analyse([__DIR__ . '/data/static-property-string-unions.php'], [
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$create.',
+				32,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz|StaticPropertyStringUnions\Foo::$create.',
+				38,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz|StaticPropertyStringUnions\Foo::$create.',
+				50,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz|StaticPropertyStringUnions\Foo::$create.',
+				58,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$create.',
+				66,
+			],
+			[
+				'Static access to instance property StaticPropertyStringUnions\Foo::$doBar.',
+				80,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$missing.',
+				118,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$missing.',
+				119,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$missing.',
+				120,
+			],
+			[
+				'Access to private property $privateProperty of class StaticPropertyStringUnions\WithNonPublic.',
+				126,
+			],
+			[
+				'Access to protected property $protectedProperty of class StaticPropertyStringUnions\WithNonPublic.',
+				127,
+			],
+		]);
+	}
+
+	#[RequiresPhp('>= 8.0.0')]
+	public function testStaticPropertyAccessOnStringUnionsWithoutCheckUnionTypes(): void
+	{
+		$this->checkUnionTypes = false;
+		$this->analyse([__DIR__ . '/data/static-property-string-unions.php'], [
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$create.',
+				32,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$create.',
+				66,
+			],
+			[
+				'Static access to instance property StaticPropertyStringUnions\Foo::$doBar.',
+				80,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$missing.',
+				118,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$missing.',
+				119,
+			],
+			[
+				'Access to an undefined static property StaticPropertyStringUnions\Baz::$missing.',
+				120,
+			],
+			[
+				'Access to private property $privateProperty of class StaticPropertyStringUnions\WithNonPublic.',
+				126,
+			],
+			[
+				'Access to protected property $protectedProperty of class StaticPropertyStringUnions\WithNonPublic.',
+				127,
+			],
+		]);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Properties/data/static-property-string-unions-assign.php b/tests/PHPStan/Rules/Properties/data/static-property-string-unions-assign.php
@@ -0,0 +1,71 @@
+<?php declare(strict_types = 1); // lint >= 8.0
+
+namespace StaticPropertyStringUnionsAssign;
+
+class Foo
+{
+
+	public static int $count = 0;
+
+	private static int $secret = 0;
+
+}
+
+class Baz
+{
+
+}
+
+trait SomeTrait
+{
+
+	public static int $traitProperty = 0;
+
+}
+
+class Runner
+{
+
+	public function writeToMissingProperty(): void
+	{
+		$class = Baz::class;
+		$class::$missing = 1;
+	}
+
+	public function incrementMissingProperty(): void
+	{
+		$class = Baz::class;
+		$class::$missing++;
+	}
+
+	public function coalesceAssignMissingProperty(): void
+	{
+		$class = Baz::class;
+		$class::$missing ??= 1;
+	}
+
+	public function writeToPrivateProperty(): void
+	{
+		$class = Foo::class;
+		$class::$secret = 1;
+	}
+
+	public function writeToUnion(bool $flag): void
+	{
+		$class = $flag ? Foo::class : Baz::class;
+		$class::$count = 1;
+	}
+
+	public function writeToExistingProperty(): void
+	{
+		$class = Foo::class;
+		$class::$count = 1;
+	}
+
+	public function writeThroughTrait(): void
+	{
+		$trait = SomeTrait::class;
+		$trait::$traitProperty = 1;
+	}
+
+}
diff --git a/tests/PHPStan/Rules/Properties/data/static-property-string-unions-asymmetric.php b/tests/PHPStan/Rules/Properties/data/static-property-string-unions-asymmetric.php
@@ -0,0 +1,19 @@
+<?php declare(strict_types = 1); // lint >= 8.5
+
+namespace StaticPropertyStringUnionsAsymmetric;
+
+class Foo
+{
+
+	public private(set) static int $privateSet = 0;
+
+	public protected(set) static int $protectedSet = 0;
+
+}
+
+function (): void {
+	$class = Foo::class;
+	$class::$privateSet = 1;
+	$class::$protectedSet = 1;
+	echo $class::$privateSet;
+};