Property can be written in get hook

Author: ondrejmirtes

src/Rules/DeadCode/UnusedPrivatePropertyRule.php

@@ -132,6 +132,10 @@ public function processNode(Node $node, Scope $scope): array
 						$methodReflection instanceof PhpMethodFromParserNodeReflection
 						&& $methodReflection->isPropertyHook()
 						&& $methodReflection->getHookedPropertyName() === $propertyName
+						&& (
+							$methodReflection->getPropertyHookName() === 'set'
+							|| $usage instanceof PropertyRead
+						)
 					) {
 						continue;
 					}

tests/PHPStan/Rules/DeadCode/UnusedPrivatePropertyRuleTest.php

@@ -387,4 +387,16 @@ public function testPropertyHooks(): void
 		]);
 	}
 
+	public function testBug12621(): void
+	{
+		if (PHP_VERSION_ID < 80400) {
+			$this->markTestSkipped('Test requires PHP 8.4.');
+		}
+
+		$this->alwaysWrittenTags = [];
+		$this->alwaysReadTags = [];
+
+		$this->analyse([__DIR__ . '/data/bug-12621.php'], []);
+	}
+
 }

tests/PHPStan/Rules/DeadCode/data/bug-12621.php

@@ -0,0 +1,21 @@
+<?php // lint >= 8.4
+
+declare(strict_types=1);
+
+namespace Bug12621;
+
+final class Test
+{
+	private string $a {
+		get => $this->a ??= $this->b;
+	}
+
+	public function __construct(
+		private readonly string $b
+	) {}
+
+	public function test(): string
+	{
+		return $this->a;
+	}
+}