We know the problem of counting the number of satisfying assignment in a given general boolean formula (CNF-SAT), a given DNF formula, or even a given 2SAT formula is a #P-complete problem.
Now, consider a CNF-SAT with no negative literal (no $\neg A$, always $A$). The decision problem is very easy (set all of the variables to TRUE and check if the assignment is satisfying the formula), but what about counting the number of satisfying assignments? Does this have a polynomial time algorithm? Or it's a #P-complete problem.