Closure with by-ref parameter is impure

Author: ondrejmirtes

src/Analyser/MutatingScope.php

@@ -1527,6 +1527,20 @@ static function (Node $node, Scope $scope) use ($arrowScope, &$arrowFunctionImpu
 				}
 			}
 
+			foreach ($parameters as $parameter) {
+				if ($parameter->passedByReference()->no()) {
+					continue;
+				}
+
+				$impurePoints[] = new ImpurePoint(
+					$this,
+					$node,
+					'functionCall',
+					'call to a Closure with by-ref parameter',
+					true,
+				);
+			}
+
 			$throwPointsForClosureType = array_map(static fn (ThrowPoint $throwPoint) => $throwPoint->isExplicit() ? SimpleThrowPoint::createExplicit($throwPoint->getType(), $throwPoint->canContainAnyThrowable()) : SimpleThrowPoint::createImplicit(), $throwPoints);
 			$impurePointsForClosureType = array_map(static fn (ImpurePoint $impurePoint) => new SimpleImpurePoint($impurePoint->getIdentifier(), $impurePoint->getDescription(), $impurePoint->isCertain()), $impurePoints);
 

tests/PHPStan/Rules/DeadCode/BetterNoopRuleTest.php

@@ -153,4 +153,9 @@ public function testBug11001(): void
 		$this->analyse([__DIR__ . '/data/bug-11001.php'], []);
 	}
 
+	public function testBug11361(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-11361.php'], []);
+	}
+
 }

tests/PHPStan/Rules/DeadCode/data/bug-11361.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Bug11361;
+
+function foo(): void
+{
+	$bar = function(&$var) {
+		$var++;
+	};
+	$a = array(0);
+	$bar($a[0]);
+}

tests/PHPStan/Rules/Pure/PureFunctionRuleTest.php

@@ -157,4 +157,14 @@ public function testFirstClassCallable(): void
 		]);
 	}
 
+	public function testBug11361(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-11361-pure.php'], [
+			[
+				'Impure call to a Closure with by-ref parameter in pure function Bug11361Pure\foo().',
+				14,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Pure/data/bug-11361-pure.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Bug11361Pure;
+
+/**
+ * @phpstan-pure
+ */
+function foo(): int
+{
+	$bar = function(&$var) {
+		$var++;
+	};
+	$a = array(0);
+	$bar($a[0]);
+
+	return 1;
+}