Bug introduced in 12.0
After upgrading to mathematica 12, this integral gives the wrong result, also with other types of similar integrals.
is wrong (it should be
E^t (-1 + t)). Such problem does not exist in previous versions.
PS, I have to use a lot of
t[i] in my program, even if I change the
[i] to subscripts, the problem is still there.