Preserve PropertyInitializationExpr for properties with default values

When entering a set hook or a method called from the constructor,
only remove PropertyInitializationExpr for properties without default
values. Properties with defaults (e.g. `private int $bar = 1`) are
always initialized, so isset() should report "not nullable nor
uninitialized" rather than just "not nullable".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

src/Analyser/MutatingScope.php

@@ -1608,7 +1608,13 @@ public function enterPropertyHook(
 		);
 
 		if ($hookName === 'set') {
-			$scope->exitPropertyInitialization($propertyName);
+			$classReflection = $this->getClassReflection();
+			if (
+				!$classReflection->hasNativeProperty($propertyName)
+				|| !$classReflection->getNativeProperty($propertyName)->getNativeReflection()->hasDefaultValue()
+			) {
+				$scope->exitPropertyInitialization($propertyName);
+			}
 		}
 
 		return $scope;

src/Analyser/NodeScopeResolver.php

@@ -721,7 +721,14 @@ public function processStmtNode(
 						if (!$expr instanceof PropertyInitializationExpr) {
 							continue;
 						}
-						$methodScope = $methodScope->exitPropertyInitialization($expr->getPropertyName());
+						$propertyName = $expr->getPropertyName();
+						if (
+							$classReflection->hasNativeProperty($propertyName)
+							&& $classReflection->getNativeProperty($propertyName)->getNativeReflection()->hasDefaultValue()
+						) {
+							continue;
+						}
+						$methodScope = $methodScope->exitPropertyInitialization($propertyName);
 					}
 				}
 			}

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -569,7 +569,7 @@ public function testBug13473(): void
 
 		$this->analyse([__DIR__ . '/data/bug-13473.php'], [
 			[
-				'Property Bug13473\FooWithDefault::$bar (int) in isset() is not nullable.',
+				'Property Bug13473\FooWithDefault::$bar in isset() is not nullable nor uninitialized.',
 				28,
 			],
 		]);
@@ -581,7 +581,7 @@ public function testBug13473Method(): void
 
 		$this->analyse([__DIR__ . '/data/bug-13473-method.php'], [
 			[
-				'Property Bug13473Method\FooWithDefault::$bar (int) in isset() is not nullable.',
+				'Property Bug13473Method\FooWithDefault::$bar in isset() is not nullable nor uninitialized.',
 				34,
 			],
 		]);