protected[this] access modifiers are deprecated and will be phased out.
Previously, these modifiers were needed for
- avoiding the generation of getters and setters
- excluding code under a
private[this]from variance checks. (Scala 2 also excludes
protected[this]but this was found to be unsound and was therefore removed).
- avoiding the generation of fields, if a
private[this] valis not accessed by a class method.
The compiler now infers for
private members the fact that they are only accessed via
this. Such members are treated as if they had been declared
protected[this] is dropped without a replacement.
This change can in some cases change the semantics of a Scala program, since a
private val is no longer guaranteed to generate a field. The field is omitted if
valis only accessed via
valis not accessed from a method in the current class.
This can cause problems if a program tries to access the missing private field via reflection. The recommended fix is to declare the field instead to be qualified private with the enclosing class as qualifier. Example:
class C(x: Int): private[C] val field = x + 1 // [C] needed if `field` is to be accessed through reflection val retained = field * field