Summary:
We previously lumped ownership predicates in with all other predicates. That limited us to a flat ownership domain.
This diff separates out the ownership predicates so we can have a richer lattice of predicates with each access path.
This lets us be more precise; for example, we can now show that
```
needToOwnBothParams(Obj o1, Obj o2) {
Obj alias;
if (*) { alias = o1; } else { alias = o2; }
alias.f = ... // both o1 and o2 need to be owned for this to be safe
}
void ownBothParamsOk() {
needToOwnBothParams(new Obj(), new Obj()); // ok, would have complained before
}
```
is safe.
Reviewed By: jberdine
Differential Revision: D5589898
fbshipit-source-id: 9606a46
Sam Blackshear