american english - "If I go.." vs. "If I will go.." referring to the future

Which one is correct?

option 1: If I go there, I can meet her

or

option 2: If I will go there, I can meet her

I clearly remember, was told by English (not American) teacher that "If", "When" cannot be used with "will" in the above context. Though, I have seen few people in US saying like option 2

I do know that "If I would go there, I could meet her" is correct (or at least, think so).

Answer

This topic seems to come up with some frequency here.
Your teacher was overgeneralizing, I'm afraid.

It's not wrong to use will this way; it's just that it may not mean what you want it to mean. In the case you mention, it means that you are commenting on the possibility that you may be willing to go there, which sounds at least odd, and seems very unlikely to be what you intend to mean.

Briefly, will is not "the future tense"; will is a modal auxiliary verb. That means it's got complicated meanings.

All modal auxiliaries like will or must have two kinds of meaning -- one logical (called "epistemic") meaning having to do with truth and probability, like

• He must be the person they mentioned.

and one social (called "deontic") meaning having to do with obligation and permission, like

• He must be home by midnight.

The reason why will is often called 'the future tense' in English classes is because it normally only uses its epistemic sense of "sposta", and that's close enough. But will also has a deontic sense of "wanna" that shows up in phrases like be willing to, will power, with a will, with the best will in the world, leave a will, etc.

What happens when you use will in a hypothetical clause is that such clauses only allow the deontic sense of will, so you wind up talking not about what's sposta happen, but about who wants to do what.

So it's perfectly OK to say

• If you will hand in your homework, I will grade it.


• Whether he will attend the concert is unknown.


• I'm not certain when he will sign it.

if you mean

• If you are willing to hand in your homework, I am willing to grade it.


• Whether he is willing to attend the concert is unknown.


• I'm not certain when he's going to get around to signing it.

But only for the deontic wanna sense, not for the usual epistemic sposta sense, of will.

Edit: I forgot to point out that this is a peculiarity of the interaction of two modals - the hypothetical clause construction and the modal auxiliary will. This is like having two strong magnetic fields together; their interactions can become, um, peculiar.

In this case some logicians might say that the deontic interpretation of will in hypotheticals is forced pragmatically because the sposta happen epistemic sense is already covered by the hypothetical construction, so using it again must mean the deontic sense. Maybe so; I'm not sure, personally.