static void retstat (LexState *ls) {
  /* stat -> RETURN [explist] [';'] */
  FuncState *fs = ls->fs;
  expdesc e;
  int nret;  /* number of values being returned */
  int first = luaY_nvarstack(fs);  /* first slot to be returned */
  if (block_follow(ls, 1) || ls->t.token == ';')
    nret = 0;  /* return no values */
  else {
    nret = explist(ls, &e);  /* optional return values */
    if (hasmultret(e.k)) {
      luaK_setmultret(fs, &e);
      if (e.k == VCALL && nret == 1 && !fs->bl->insidetbc) {  /* tail call? */
        SET_OPCODE(getinstruction(fs,&e), OP_TAILCALL);
        lua_assert(GETARG_A(getinstruction(fs,&e)) == luaY_nvarstack(fs));
      }
      nret = LUA_MULTRET;  /* return all values */
    }
    else {
      if (nret == 1)  /* only one single value? */
        first = luaK_exp2anyreg(fs, &e);  /* can use original slot */
      else {  /* values must go to the top of the stack */
        luaK_exp2nextreg(fs, &e);
        lua_assert(nret == fs->freereg - first);
      }
    }
  }
  luaK_ret(fs, first, nret);
  testnext(ls, ';');  /* skip optional semicolon */
}