Use TypeTraverser::map for nested array type in maybe-array input paths

Replace conservative `array<mixed, mixed>` with precise nested array
type computation using TypeTraverser::map when input type carries array
structure information (e.g., `int|array<int>`).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

src/Type/Php/FilterFunctionReturnTypeHelper.php

@@ -193,7 +193,8 @@ public function getType(Type $inputType, ?Type $filterType, ?Type $flagsType): T
 
 		if ($hasRequireArrayFlag->yes()) {
 			if (!$inputIsArray->no()) {
-				$type = TypeCombinator::union($type, new ArrayType($mixedType, $mixedType));
+				$nestedArrayType = $this->computeNestedArrayType($inputType, $filterType, $flagsType, $mixedType);
+				$type = TypeCombinator::union($type, $nestedArrayType);
 			}
 			$type = new ArrayType($mixedType, $type);
 			if (!$inputIsArray->yes()) {
@@ -203,7 +204,8 @@ public function getType(Type $inputType, ?Type $filterType, ?Type $flagsType): T
 
 		if ($hasRequireArrayFlag->no() && $hasForceArrayFlag->yes()) {
 			if (!$inputIsArray->no()) {
-				$type = TypeCombinator::union($type, new ArrayType($mixedType, $mixedType));
+				$nestedArrayType = $this->computeNestedArrayType($inputType, $filterType, $flagsType, $mixedType);
+				$type = TypeCombinator::union($type, $nestedArrayType);
 			}
 			return new ArrayType($mixedType, $type);
 		}
@@ -252,6 +254,26 @@ private function filterScalarType(Type $inputType, int $filterValue, Type $defau
 		return $type;
 	}
 
+	/**
+	 * Computes the nested array type for the array portion of a maybe-array input.
+	 * Uses TypeTraverser to extract array components and recursively filter them.
+	 */
+	private function computeNestedArrayType(Type $inputType, ?Type $filterType, ?Type $flagsType, MixedType $mixedType): Type
+	{
+		return TypeTraverser::map($inputType, function (Type $type, callable $traverse) use ($filterType, $flagsType, $mixedType): Type {
+			if ($type instanceof UnionType || $type instanceof IntersectionType) {
+				return $traverse($type);
+			}
+			if ($type->isArray()->yes()) {
+				return $this->getType($type, $filterType, $flagsType);
+			}
+			if ($type->isArray()->maybe()) {
+				return new ArrayType($mixedType, $mixedType);
+			}
+			return new NeverType();
+		});
+	}
+
 	/**
 	 * @return array<int, Type>
 	 */

tests/PHPStan/Analyser/nsrt/bug-11339.php

@@ -60,3 +60,33 @@ function typedArrayInputs(array $arrayOfInt, array $arrayOfArrayOfInt, array $ar
 	$s = filter_var($arrayOfArrayOfInt, FILTER_VALIDATE_INT, ['flags' => FILTER_FORCE_ARRAY]);
 	assertType('array<array<int>>', $s);
 }
+
+/**
+ * Union-typed inputs (scalar | array) exercise the inputIsArray->maybe() path
+ *
+ * @param int|array<int> $intOrArrayOfInt
+ * @param string|array<string> $stringOrArrayOfString
+ */
+function unionTypedInputs(int|array $intOrArrayOfInt, string|array $stringOrArrayOfString): void
+{
+	// FORCE_ARRAY: scalar part filtered, array part recursively filtered
+	$a = filter_var($intOrArrayOfInt, FILTER_VALIDATE_INT, ['flags' => FILTER_FORCE_ARRAY]);
+	assertType('array<array<int>|int|false>', $a);
+
+	$b = filter_var($stringOrArrayOfString, FILTER_DEFAULT, ['flags' => FILTER_FORCE_ARRAY]);
+	assertType('array<array<string>|string|false>', $b);
+
+	// REQUIRE_ARRAY: scalar input returns false, array input recursively filtered
+	$c = filter_var($intOrArrayOfInt, FILTER_VALIDATE_INT, ['flags' => FILTER_REQUIRE_ARRAY]);
+	assertType('array<array<int>|int|false>|false', $c);
+
+	$d = filter_var($stringOrArrayOfString, FILTER_DEFAULT, ['flags' => FILTER_REQUIRE_ARRAY]);
+	assertType('array<array<string>|string|false>|false', $d);
+
+	// REQUIRE_ARRAY with NULL_ON_FAILURE
+	$e = filter_var($intOrArrayOfInt, FILTER_VALIDATE_INT, ['flags' => FILTER_REQUIRE_ARRAY|FILTER_NULL_ON_FAILURE]);
+	assertType('array<array<int>|int|null>|null', $e);
+
+	$f = filter_var($stringOrArrayOfString, FILTER_DEFAULT, ['flags' => FILTER_REQUIRE_ARRAY|FILTER_NULL_ON_FAILURE]);
+	assertType('array<array<string>|string|null>|null', $f);
+}