Fix array_filter that does not return all items

Author: ondrejmirtes

src/Type/Php/ArrayFilterFunctionReturnTypeReturnTypeExtension.php

@@ -21,6 +21,7 @@
 use PHPStan\Type\BenevolentUnionType;
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantArrayTypeBuilder;
+use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\DynamicFunctionReturnTypeExtension;
 use PHPStan\Type\MixedType;
 use PHPStan\Type\NeverType;
@@ -170,12 +171,12 @@ private function filterByTruthyValue(Scope $scope, Error|Variable|null $itemVar,
 				$builder = ConstantArrayTypeBuilder::createEmpty();
 				foreach ($constantArray->getKeyTypes() as $i => $keyType) {
 					$itemType = $constantArray->getValueTypes()[$i];
-					[$newKeyType, $newItemType] = $this->processKeyAndItemType($scope, $keyType, $itemType, $itemVar, $keyVar, $expr);
+					[$newKeyType, $newItemType, $optional] = $this->processKeyAndItemType($scope, $keyType, $itemType, $itemVar, $keyVar, $expr);
 					if ($newKeyType instanceof NeverType || $newItemType instanceof NeverType) {
 						continue;
 					}
 					if ($itemType->equals($newItemType) && $keyType->equals($newKeyType)) {
-						$builder->setOffsetValueType($keyType, $itemType);
+						$builder->setOffsetValueType($keyType, $itemType, $optional);
 						continue;
 					}
 
@@ -198,7 +199,7 @@ private function filterByTruthyValue(Scope $scope, Error|Variable|null $itemVar,
 	}
 
 	/**
-	 * @return array{Type, Type}
+	 * @return array{Type, Type, bool}
 	 */
 	private function processKeyAndItemType(MutatingScope $scope, Type $keyType, Type $itemType, Error|Variable|null $itemVar, Error|Variable|null $keyVar, Expr $expr): array
 	{
@@ -220,11 +221,13 @@ private function processKeyAndItemType(MutatingScope $scope, Type $keyType, Type
 			$scope = $scope->assignVariable($keyVarName, $keyType);
 		}
 
+		$booleanResult = $scope->getType($expr)->toBoolean();
 		$scope = $scope->filterByTruthyValue($expr);
 
 		return [
 			$keyVarName !== null ? $scope->getVariableType($keyVarName) : $keyType,
 			$itemVarName !== null ? $scope->getVariableType($itemVarName) : $itemType,
+			!$booleanResult instanceof ConstantBooleanType,
 		];
 	}
 

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -1007,6 +1007,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6170.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/../Rules/Arrays/data/slevomat-foreach-array-key-exists-bug.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/array-key-exists.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-7909.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/bug-7909.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Bug7909;
+
+use function PHPStan\Testing\assertType;
+
+function (): void {
+	$filenames = array_filter(['file1', 'file2'], 'file_exists');
+	assertType("array{0?: 'file1', 1?: 'file2'}", $filenames);
+};