终于找到明确答案了。简而言之是可以claim的。具体依据在pub 519第56页，专门有一
段标题是Student, Apprentices, Trainees, Teachers, Professors, and
Researchers Who Became Resident Aliens.
里面先提到
Generally, you must be a nonresident alien student ... in order to claim a
tax treaty exemption ... once you become a resident alien, you generally can
no longer claim a tax treaty exemption for this income.
接着下一段说
However, if you entered the United states as a nonresident alien, but you
are now a resident alien for US tax purposes, the treaty exemption will
continue to apply if the tax treaty's saving clause provides an exception
for it and you otherwise meet the requirements...
特别注意的是下面一段专门说道
Soe exeptions to the saving cluse apply to all resident aliens (FOR EXAMPLE
US-PEOPLE'S REPUBLIC OF CHINA TREATY); OTHERS apply only to resident aliens
who are not lawful permanent residents of the United States (green card
holders).
所以非常明确，是可以claim的！这下放心了。希望对后来人有帮助。
