claim后接不定式，意为声称某事是真实的。如果不定式用to do形式，则通常不定式为静态动词，表示声称时的状态。例如：
He claims to know nothing about the robbery.
He claims to be an expert.
如果不定式为动态动词表示事件意义，则该事件一定是之前发生过的，所以不定式用完成体to have done形式。例如：
He claimed to have served under seven presidents since entering the Senate at 29.
I never claimed to have never made mistakes.
