mkTcForAllCos tvs co            = ASSERT( all isTyVar tvs ) foldr TcForAllCo co tvs
mkTcForAllCos tvs co            = ASSERT( all isTyVar tvs ) foldr TcForAllCo co tvs
mkTcForAllCos tvs co            = ASSERT( all isTyVar tvs ) foldr TcForAllCo co tvs