SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "f"
    GENERIC_PARAM_LIST
      L_ANGLE "<"
      TYPE_PARAM
        NAME
          IDENT "T"
      R_ANGLE ">"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    WHERE_CLAUSE
      WHERE_KW "where"
      WHITESPACE " "
      WHERE_PRED
        PATH_TYPE
          PATH
            PATH_SEGMENT
              NAME_REF
                IDENT "T"
        COLON ":"
        WHITESPACE " "
        TYPE_BOUND_LIST
          TYPE_BOUND
            PATH_TYPE
              PATH
                PATH_SEGMENT
                  NAME_REF
                    IDENT "Fn"
                  PARENTHESIZED_ARG_LIST
                    L_PAREN "("
                    R_PAREN ")"
                  WHITESPACE " "
                  RET_TYPE
                    THIN_ARROW "->"
                    WHITESPACE " "
                    PATH_TYPE
                      PATH
                        PATH_SEGMENT
                          NAME_REF
                            IDENT "u8"
          WHITESPACE " "
          PLUS "+"
          WHITESPACE " "
          TYPE_BOUND
            PATH_TYPE
              PATH
                PATH_SEGMENT
                  NAME_REF
                    IDENT "Send"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        R_CURLY "}"
  WHITESPACE "\n"
