src/Language/Visitor.php
public static function visitWithTypeInfo(TypeInfo $typeInfo, $visitor)
    {
        return [
            'enter' => static function (Node $node) use ($typeInfo, $visitor) {
                $typeInfo->enter($node);
                $fn = self::getVisitFn($visitor, $node->kind, false);

                if ($fn) {
                    $result = call_user_func_array($fn, func_get_args());
                    if ($result !== null) {
                        $typeInfo->leave($node);
                        if ($result instanceof Node) {
                            $typeInfo->enter($result);
                        }
                    }

                    return $result;
                }

                return null;
            },
            'leave' => static function (Node $node) use ($typeInfo, $visitor) {
                $fn     = self::getVisitFn($visitor, $node->kind, true);
                $result = $fn ? call_user_func_array($fn, func_get_args()) : null;
                $typeInfo->leave($node);

                return $result;
            },
        ];
    }
public static function visitWithTypeInfo(TypeInfo $typeInfo, $visitor)
    {
        return [
            'enter' => static function (Node $node) use ($typeInfo, $visitor) {
                $typeInfo->enter($node);
                $fn = self::getVisitFn($visitor, $node->kind, false);

                if ($fn) {
                    $result = call_user_func_array($fn, func_get_args());
                    if ($result !== null) {
                        $typeInfo->leave($node);
                        if ($result instanceof Node) {
                            $typeInfo->enter($result);
                        }
                    }

                    return $result;
                }

                return null;
            },
            'leave' => static function (Node $node) use ($typeInfo, $visitor) {
                $fn     = self::getVisitFn($visitor, $node->kind, true);
                $result = $fn ? call_user_func_array($fn, func_get_args()) : null;
                $typeInfo->leave($node);

                return $result;
            },
        ];
    }
Creates a new visitor instance which maintains a provided TypeInfo instance
along with visiting visitor.