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The predicates `getter` and `setter` in `StructLikeClass.qll` were very slow on some snapshots. On https://github.com/dotnet/coreclr they had this performance: StructLikeClass::getter#fff#antijoin_rhs ........... 3m55s Variable::Variable::getAnAssignedValue_dispred#bb .. 3m36s StructLikeClass::setter#fff#antijoin_rhs ........... 20.5s The `getAnAssignedValue_dispred` predicate in the middle was slow due to magic propagated from `setter`. With this commit, performance is instead: StructLikeClass::getter#fff#antijoin_rhs ........... 497ms Variable::Variable::getAnAssignedValue_dispred#ff .. 617ms StructLikeClass::setter#fff#antijoin_rhs ........... 158ms Instead of hand-optimizing the QL for performance, I simplified `setter` and `getter` to require slightly stronger conditions. Previously, a function was only considered a setter if it had no writes to other fields on the same class. That requirement is now relaxed by dropping the "on the same class" part. I made the corresponding change for what defines a getter. I think that still captures the spirit of what getters and setters are. I also changed the double-negation with `exists` into a `forall`.