Function checktab

third-party/lua-5.5.0/src/ltablib.c:47–59

** Check that 'arg' either is a table or can behave like one (that is, ** has a metatable with the required metamethods) */

** has a metatable with the required metamethods)
*/
static void checktab (lua_State *L, int arg, int what) {
  if (lua_type(L, arg) != LUA_TTABLE) {  /* is it not a table? */
    int n = 1;  /* number of elements to pop */
    if (lua_getmetatable(L, arg) &&  /* must have metatable */
        (!(what & TAB_R) || checkfield(L, "__index", ++n)) &&
        (!(what & TAB_W) || checkfield(L, "__newindex", ++n)) &&
        (!(what & TAB_L) || checkfield(L, "__len", ++n))) {
      lua_pop(L, n);  /* pop metatable and tested metamethods */
    }
    else
      luaL_checktype(L, arg, LUA_TTABLE);  /* force an error */
  }
}


static int tcreate (lua_State *L) {