SOURCE_FILE
  IMPL
    IMPL_KW "impl"
    WHITESPACE " "
    BANG "!"
    PATH_TYPE
      PATH
        PATH_SEGMENT
          NAME_REF
            IDENT "Send"
    WHITESPACE " "
    FOR_KW "for"
    WHITESPACE " "
    PATH_TYPE
      PATH
        PATH_SEGMENT
          NAME_REF
            IDENT "S"
    WHITESPACE " "
    ASSOC_ITEM_LIST
      L_CURLY "{"
      R_CURLY "}"
  WHITESPACE "\n"
