$title infeas: infeasible linear program

set index_set/i1, i2/;

positive variable x(index_set);
variable profit;

equation
	objective       "define cost"
        constraint      "a single constraint"
;

objective..
	profit =e= 2*x('i1') + 3*x('i2');

constraint..
	sum(index_set, x(index_set)) =l= -1.0;

model infeas/all/;

* the problem is infeasible - there is no vector x satisfying the constraints
solve infeas using lp maximizing profit;