
Originally Posted by
aggelos
Actually, will is possible in an 'if'-clause in the following cases:
-In conditional clauses, when it means wish, not mind, insist on: Sit here if you will. - I'll do the dishes if you will do the cleaning. - If she will (will emphasized) eat so much, it's no wonder she can't get rid of all those extra pounds. But it would be wrong to say, for example: I'll stay at home if it will rain.
-In reported questions: He wants to know if you will be here tomorrow. incorrect
- I don't know if they'll believe you. -incorrect
Whether could also be used here instead of if.
The same is more or less true with would in 2nd conditionals, as well as in reported questions in the past.