word formation - Is there a rule for when contractions are not possible?

In conversing with non-native English speakers online, I saw someone type:

Do you know who ****I’m*** ?

This is obviously wrong to a native English speaker, but I don’t know why. Is there a rule that tells when contractions are not allowed?

Here are some more similar examples where the contraction doesn’t work (with the expansion of the contraction in parentheses following each):

• Can you tell who **I’m* by my voice alone? (I am)




• Please, tell me who **he’s/she’s/they’re*. (he is/she is/they are)





• If you want to go to the movie, **we’ll.* (we will)




• Will you have some? Yes, **I’ll.* (I will)




• I won’t have any, but tell me if **you’ll*. (you will)




• I didn’t have the same thing for supper as **you’d.* (you had)




• Would you like to go? Sure **I’d.* (I would)