Fix property assign not being an impure point in arrow function

src/Analyser/MutatingScope.php

@@ -1272,17 +1272,38 @@ private function resolveType(string $exprString, Expr $node): Type
 					}
 				}
 
+				$arrowFunctionImpurePoints = [];
+				$invalidateExpressions = [];
 				$arrowFunctionExprResult = $this->nodeScopeResolver->processExprNode(
 					new Node\Stmt\Expression($node->expr),
 					$node->expr,
 					$arrowScope,
-					static function (): void {
+					static function (Node $node, Scope $scope) use ($arrowScope, &$arrowFunctionImpurePoints, &$invalidateExpressions): void {
+						if ($scope->getAnonymousFunctionReflection() !== $arrowScope->getAnonymousFunctionReflection()) {
+							return;
+						}
+
+						if ($node instanceof InvalidateExprNode) {
+							$invalidateExpressions[] = $node;
+							return;
+						}
+
+						if (!$node instanceof PropertyAssignNode) {
+							return;
+						}
+
+						$arrowFunctionImpurePoints[] = new ImpurePoint(
+							$scope,
+							$node,
+							'propertyAssign',
+							'property assignment',
+							true,
+						);
 					},
 					ExpressionContext::createDeep(),
 				);
 				$throwPoints = $arrowFunctionExprResult->getThrowPoints();
-				$impurePoints = $arrowFunctionExprResult->getImpurePoints();
-				$invalidateExpressions = [];
+				$impurePoints = array_merge($arrowFunctionImpurePoints, $arrowFunctionExprResult->getImpurePoints());
 				$usedVariables = [];
 			} else {
 				$closureScope = $this->enterAnonymousFunctionWithoutReflection($node, $callableParameters);

tests/PHPStan/Rules/DeadCode/BetterNoopRuleTest.php

@@ -6,6 +6,7 @@
 use PHPStan\Node\Printer\Printer;
 use PHPStan\Rules\Rule;
 use PHPStan\Testing\RuleTestCase;
+use const PHP_VERSION_ID;
 
 /**
  * @extends RuleTestCase<BetterNoopRule>
@@ -145,6 +146,10 @@ public function testRuleImpurePoints(): void
 
 	public function testBug11001(): void
 	{
+		if (PHP_VERSION_ID < 70400) {
+			self::markTestSkipped('Test requires PHP 7.4.');
+		}
+
 		$this->analyse([__DIR__ . '/data/bug-11001.php'], []);
 	}
 

tests/PHPStan/Rules/DeadCode/data/bug-11001.php

@@ -21,3 +21,18 @@ public function doFoo(): void
 	}
 
 }
+
+class Foo2
+{
+	public function test(): void
+	{
+		\Closure::bind(fn () => $this->status = 5, $this)();
+	}
+
+	public function test2(): void
+	{
+		\Closure::bind(function () {
+			$this->status = 5;
+		}, $this)();
+	}
+}