What a mistake (it is) to have refused his invitation.
问题描述：
What a mistake (it is) to have refused his invitation.
to have refused his invitation在句子中作什么成分?
答
to have refused his invitation在此句子中是真正的主语,it是形式宾语.将此感叹句改为陈述句是：It is a mistake to have refused his invitation.之所以用感叹句,其目的是此错误之大,遗憾之深.例如：
What a pity (it is) to have missed the wonderful film.感觉像定语，感觉又像形式宾语。