Update array_filter signature in PHP 8.0 to allow null as callback

src/Reflection/ParametersAcceptorSelector.php

@@ -171,13 +171,16 @@ public static function selectFromArgs(
 				$parameters[1] = new NativeParameterReflection(
 					$parameters[1]->getName(),
 					$parameters[1]->isOptional(),
-					new CallableType(
-						$arrayFilterParameters ?? [
-							new DummyParameter('item', $scope->getIterableValueType($scope->getType($args[0]->value)), false, PassedByReference::createNo(), false, null),
-						],
-						new MixedType(),
-						false,
-					),
+					new UnionType([
+						new CallableType(
+							$arrayFilterParameters ?? [
+								new DummyParameter('item', $scope->getIterableValueType($scope->getType($args[0]->value)), false, PassedByReference::createNo(), false, null),
+							],
+							new MixedType(),
+							false,
+						),
+						new NullType(),
+					]),
 					$parameters[1]->passedByReference(),
 					$parameters[1]->isVariadic(),
 					$parameters[1]->getDefaultValue(),

tests/PHPStan/Analyser/AnalyserIntegrationTest.php

@@ -1239,7 +1239,7 @@ public function testBug9994(): void
 		$errors = $this->runAnalyse(__DIR__ . '/data/bug-9994.php');
 		$this->assertCount(2, $errors);
 		$this->assertSame('Negated boolean expression is always false.', $errors[0]->getMessage());
-		$this->assertSame('Parameter #2 $callback of function array_filter expects callable(1|2|3|null): mixed, false given.', $errors[1]->getMessage());
+		$this->assertSame('Parameter #2 $callback of function array_filter expects (callable(1|2|3|null): mixed)|null, false given.', $errors[1]->getMessage());
 	}
 
 	public function testBug10049(): void

tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

@@ -868,15 +868,15 @@ public function testArrayFilterCallback(bool $checkExplicitMixed): void
 		$this->checkExplicitMixed = $checkExplicitMixed;
 		$errors = [
 			[
-				'Parameter #2 $callback of function array_filter expects callable(int): mixed, Closure(string): true given.',
+				'Parameter #2 $callback of function array_filter expects (callable(int): mixed)|null, Closure(string): true given.',
 				17,
 			],
 		];
 		if ($checkExplicitMixed) {
 			$errors[] = [
-				'Parameter #2 $callback of function array_filter expects callable(mixed): mixed, Closure(int): true given.',
+				'Parameter #2 $callback of function array_filter expects (callable(mixed): mixed)|null, Closure(int): true given.',
 				20,
-				'Type int of parameter #1 $i of passed callable needs to be same or wider than parameter type mixed of accepting callable.',
+				'Type #1 from the union: Type int of parameter #1 $i of passed callable needs to be same or wider than parameter type mixed of accepting callable.',
 			];
 		}
 		$this->analyse([__DIR__ . '/data/array_filter_callback.php'], $errors);
@@ -1549,4 +1549,13 @@ public function testBug9793(): void
 		$this->analyse([__DIR__ . '/data/bug-9793.php'], $errors);
 	}
 
+	public function testCallToArrayFilterWithNullCallback(): void
+	{
+		if (PHP_VERSION_ID < 80000) {
+			$this->markTestSkipped('Test requires PHP 8.0');
+		}
+
+		$this->analyse([__DIR__ . '/data/array_filter_null_callback.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Functions/data/array_filter_null_callback.php

@@ -0,0 +1,3 @@
+<?php
+
+array_filter([], null);