In file included from /Users/andy2/workspace/OpenTTD.OpenTTD/src/ai/ai_instance.cpp:82:

/Users/andy2/workspace/OpenTTD.OpenTTD/src/ai/../company_base.h:119:12: error:

      field has incomplete type 'RailTypes'

        RailTypes avail_railtypes;         ///< Rail types available to ...

                  ^

/Users/andy2/workspace/OpenTTD.OpenTTD/src/ai/../rail_type.h:53:6: note:

      forward declaration of 'RailTypes'

enum RailTypes : uint64 {