[clang] [AST] Only dump desugared type when visibly different (PR #65214)

[Jessica Clarke via cfe-commits]

jrtc27 wrote:

> > > So it looks like some of these changes undo some of the change introduced by @mizvekov in some tests. Maybe @zygoloid or @AaronBallman has some more input here.
> > 
> > 
> > Do you have a pointer to such changes?
> 
> One of the commits is here: [15f3cd6](https://github.com/llvm/llvm-project/commit/15f3cd6bfc670ba6106184a903eb04be059e5977)
> 
> I know he did a lot of work in this area and I am not familiar with it in detail but I want to make sure interested parties are not stepping on each others work.

My view is that the `'struct S':'struct S'` is just an unintended side-effect of adding that sugar. I'm not removing that sugar, and in cases where the as-written type differs from the desugared type it will still print both, it just doesn't print both when textually there is no difference.

https://github.com/llvm/llvm-project/pull/65214