SOURCE_FILE
  IMPL
    IMPL_KW "impl"
    WHITESPACE " "
    PATH_TYPE
      PATH
        PATH_SEGMENT
          NAME_REF
            IDENT "S"
    WHITESPACE " "
    ASSOC_ITEM_LIST
      L_CURLY "{"
      WHITESPACE " "
      ATTR
        POUND "#"
        BANG "!"
        L_BRACK "["
        META
          PATH
            PATH_SEGMENT
              NAME_REF
                IDENT "attr"
        R_BRACK "]"
      WHITESPACE " "
      R_CURLY "}"
  WHITESPACE "\n"
