SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "f"
    PARAM_LIST
      L_PAREN "("
      SELF_PARAM
        ATTR
          POUND "#"
          L_BRACK "["
          META
            PATH
              PATH_SEGMENT
                NAME_REF
                  IDENT "must_use"
          R_BRACK "]"
        WHITESPACE " "
        NAME
          SELF_KW "self"
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        R_CURLY "}"
  WHITESPACE "\n"
