it's nice talking to you~
it's nice doing sth.
这里it是形式主语,代表doing sth.
同样,it作为形式主语也可以代表 to do sth.
于是也可以说成 it's nice to talk to you.当然语法是对的,只是两个to有点拗口.你可以说it's nice to meet you.