// return the Lua table at 'idx' as a copied Go map. If 't' is nil then the map
// type is map[string]interface{}
func CopyTableToMap(L *lua.State, t reflect.Type, idx int) interface{} {
	if t == nil {
		t = reflect.TypeOf(tmap)
	}
	te, tk := t.Elem(), t.Key()
	m := reflect.MakeMap(t)
	L.PushNil()
	if idx < 0 {
		idx--
	}
	for L.Next(idx) != 0 {
		// key at -2, value at -1
		key := valueOf(LuaToGo(L, tk, -2))
		val := valueOf(LuaToGo(L, te, -1))
		m.SetMapIndex(key, val)
		L.Pop(1)
	}
	return m.Interface()
}
func CopyTableToStruct(L *lua.State, t reflect.Type, idx int) interface{} {
	if t.Kind() == reflect.Ptr {
		t = t.Elem()
	}
	s := reflect.New(t) // T -> *T
	ref := s.Elem()
	L.PushNil()
	if idx < 0 {
		idx--
	}
	for L.Next(idx) != 0 {
		key := L.ToString(-2)
		f := ref.FieldByName(key)
		if f.IsValid() {
			val := valueOf(LuaToGo(L, f.Type(), -1))
			f.Set(val)
		}
		L.Pop(1)
	}
	return s.Interface()
}