Is there a difference in meaning between "haven't ever" and "have never":
- Haven't you ever tried this?
- Have you never tried this?
And in such structure.
- You haven't ever tried this?
- You have never tried this?
Using a negative interrogative structure is a (usually spoken) form which communicates that you expect a certain answer, that you have already formed an opinion on the subject.
Do you speak Portuguese?
Have you ever eaten ice cream before?
Is it raining?
These are all neutral questions, I am not communicating an opinion about the answer.
If I say:
Don't you speak Portuguese?
Haven't you eaten ice cream before?
Isn't it raining?
Then you can tell I already have an opinion about those questions. Usually it means that I think the answer is yes.
Sue: "Maria is coming over, but she doesn't speak English so it might be difficult"
Mike: "John, don't you speak Portuguese? You could help her out, right?"
John: "Yes, I do, that'll be no problem?"
Here John knows that Mike thinks that John speaks Portuguese, but wants John to confirm. If Mike said "John, do you speak Portuguese" then John doesn't know that mike thinks the answer is yes.
"I'm going out for a walk."
"But isn't it raining?"
Here, isn't it raining? means I think it's raining, am I right?
The other meaning it can have is to express surprise at a piece of information. Similar to the above, but rather than saying "I think the answer is yes" You're saying "It's very surprising that the answer to this question is no!", and it allows the other person to confirm.
So, a bit of a silly example:
"Wow! This is delicious, what is it?"
"Haven't you ever tried ice cream before???"
In this example, I am surprised that he has never tried ice cream, so I am not just asking the question, I am communicating that I will be very surprised if the answer is no.
A very similar structure is like this:
You speak Portuguese, don't you?
You've eaten ice cream before, haven't you?
It's raining, isn't it?