stableNull

An annotation that can be used to mark a mutable field as trackable for nullability. With explicit nulls, a normal mutable field cannot be tracked for nullability by flow typing, since it can be updated to a null value at the same time. This annotation will force the compiler to track the field for nullability, as long as the prefix is a stable path. See tests/explicit-nulls/pos/force-track-var-fields.scala for an example.