Summary:
Before, we were using a set domain of strings to model a boolean domain.
An explicit boolean domain makes it a bit clear what's going on.
There are two things to note here:
(1) This actually changed the semantics from the old set domain. The set domain wouldn't warn if the lock is held on only one side of a branch, which isn't what we want.
(2) We can't actually test this because the modeling for `Lock.lock()` etc doesn't work :(.
The reason is that the models (which do things like adding attributes for `Lock.lock`) are analyzed for Infer, but not for the checkers.
We'll have to add separate models for thread safety.
Reviewed By: peterogithub
Differential Revision: D4242487
fbshipit-source-id: 9fc599d
Sam Blackshear