Some rules of contractions in English

Sometimes in written and spoken English we contract words.

Examples

  1. A: You should go to France.
    B: I will one day.
    Not I'll one day
  2. A: You can not do that
    B: Can't I? / Can I not?
    Not Can't I?

Spelling

Contractions must match spelling rules and not follow speech too literally. so: I want to do that
Not I wanna do that

Here the contraction is common and acceptable in spoken English but not good in written English.