Loop bounds changed in loop

[Beliavsky]

Since the # of iterations in a loop is set at the beginning of the loop, the code

implicit none
integer :: i, n
n = 3
do i=1,n
   n = n-1
   print*,i,n
end do
end

is valid, giving

           1           2
           2           1
           3           0

but it is confusing, so fortitude could warn about reassigning loop bound variables within a loop.