I have just downloaded last MinGW and I get these errors that I also got before updating:
CoWork.h:159:11: error: 'result_of_t' is not a member of 'std'
CoWork.h:159:28: error: 'decay_t' is not a member of 'std'
This is caused by having common c++ flag "c++=11". Should be "c++=14".
Which is weird - I have just checked how methods are set by default after downloading U++ and it is set correctly. Perhaps you are using some older build methods?