Summary:
RacerD is angelic in the sense that when a method has no summary, no accesses are added to the symbolic state when we call that method. However, when the method returns an object we then proceed to access, this leads to non-angelic behaviour: if the object is assumed to be un-owned, then the accesses may lead to a race.
This manifests itself on Litho components, which are generated code without sources and thus RacerD has no CFG to analyse, and therefore produces no summary. The `Builder` patterns used in these classes are ubiquitous, and full of spurious races due to the fact that the returned objects, even though freshly allocated, are un-owned as far as RacerD knows.
Here, instead of going full-angelic and assuming that every method without a summary returns an owned object (which is a bit extreme), we try to model the `Builder` pattern wrt ownership. That is, static `create` methods returning `Builder` types are assumed to return full ownership; and, non-static methods of a `Builder` class which return the same type as their receiver are assumed to return conditional ownership.
Reviewed By: ezgicicek
Differential Revision: D18748423
fbshipit-source-id: bd53d4b67
Nikos Gorogiannis
ea645cceab
