I'm not sure when to use the phrase "that's not gonna happen". Does it mean it actually will never happen? I think using "not gonna happen" implies that I'm going to do the best I can to keep it from happening. Here's my simple context: So, for example, my friend said "I don't want you to turn into a stranger". Would it sound natural if I said " that's not gonna happen"? Thanks so much
It would sound natural to say "That's not gonna happen" when your friend says "I don't want you to turn into a stranger."
"That's not gonna happen" is known as a "colloquialism". It's an informal phrase that would almost never be interpreted literally. It is, however, something that does imply, as you've stated, that you will do your best to ensure it doesn't occur.