Fix phpstan/phpstan#13473: isset() false positive in property set hook

- In property set hooks, the hooked property might not be initialized yet
  (e.g., when the set hook is triggered from __construct())
- Removed PropertyInitializationExpr for the hooked property from the scope
  when entering a set hook in MutatingScope::enterPropertyHook()
- Added regression test in tests/PHPStan/Rules/Variables/data/bug-13473.php

Author: VincentLanglet

src/Analyser/MutatingScope.php

@@ -1574,7 +1574,7 @@ public function enterPropertyHook(
 
 		$realParameterTypes = $this->getRealParameterTypes($hook);
 
-		return $this->enterFunctionLike(
+		$scope = $this->enterFunctionLike(
 			new PhpMethodFromParserNodeReflection(
 				$this->getClassReflection(),
 				$hook,
@@ -1606,6 +1606,14 @@ public function enterPropertyHook(
 			),
 			true,
 		);
+
+		if ($hookName === 'set') {
+			$initExprKey = $this->getNodeKey(new PropertyInitializationExpr($propertyName));
+			unset($scope->expressionTypes[$initExprKey]);
+			unset($scope->nativeExpressionTypes[$initExprKey]);
+		}
+
+		return $scope;
 	}
 
 	private function transformStaticType(Type $type): Type

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -562,4 +562,12 @@ public function testBug14393(): void
 		]);
 	}
 
+	#[RequiresPhp('>= 8.4')]
+	public function testBug13473(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+
+		$this->analyse([__DIR__ . '/data/bug-13473.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Variables/data/bug-13473.php

@@ -0,0 +1,22 @@
+<?php // lint >= 8.4
+
+declare(strict_types = 1);
+
+namespace Bug13473;
+
+class Foo {
+	private(set) int $bar {
+		get => $this->bar;
+		set(int $bar) {
+			if (isset($this->bar)) {
+				throw new \Exception('bar is set');
+			}
+			$this->bar = $bar;
+		}
+	}
+
+	public function __construct(int $bar)
+	{
+		$this->bar = $bar;
+	}
+}