[clang] [clang][analyzer] CallAndMessage warnings at pointer to uninitialized struct (PR #164600)

[Balazs Benics via cfe-commits]

steakhal wrote:

> In general, I tend to notice a pattern that `LazyCompoundVal` is too opaque and its performance benefits come with lots of added code complexity as we always need to explicitly check for it. (However I don't know enough, perhaps this is still the least wrong approach.)

LCVs are complicated. However, having nonloc::CompoundVals only make this worse. If I had to choose today, I'd only have LCVs for representing compount vals. But note that I have a strong believe that LCVs are necessary for their laziness. I'm pretty sure though that we could have nice APIs around it that would bring consistency and no surprises.

https://github.com/llvm/llvm-project/pull/164600