if/then/else unexpected behavior

When we wrote 
value = if (test) {v1} else {0.0} - v2;
We expect to have something equals to if (test) {v1 - v2} else {- v2} but it's equals to if (test) {v1} else {- v2};
A message should warn to use parentheses when if/then/else is used with operators .  