Bug introduced in 12.0 and fixed in 12.1
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.