It was impossible for lost time to be made up这句话的结构

问题描述:

It was impossible for lost time to be made up这句话的结构
请问这句话是什么结构
主语是什么,是不定式还是lost time?我看的材料说是不定式做主语成分

it 做形式主语,to be made up是不定式做后置定语修饰 lost time.
原句可以理解为 making up the lost time was impossible
lost time to be made up整个做主语,强调弥补这个动作