Having a nonstandard American dialect is even worse. Texas dialects have a much broader set of larger contractions than coastal and Midwest accents. Autocorrect becomes an active enemy when I'm trying to type "I'd'nt've" or "y'couldn't'v'nt'd".
This must be the first time I'm on Autocorrect's side ;->
"y'couldn't'v'nt'd" to me sounds like "you couldn't have unted", which is true as I've never "unted" anything in my life.
I guess "I'd'nt've" means "I don't have", but in British English we'd still write that as "I don' 'av'" (as we'd also drop the t).
I would -> I'd
would not -> wouldn't
So "I would not" -> "I'dn't"?
As a British English speaker, I can't even guess what verb they're trying to say that they wouldn't / couldn't have done.
I guess "I'd'nt've" means "I don't have"
I think it meant 'I would not have', not "I don't have".