Defines an implicit Message[A] for any type A <: AnyRef unless overridden by a higher-priority conversion of type implicit def bMessage[A <: B]: Message[A]
PureMessage, which means that an object of type A is assumed NOT to carry resources, that should be cleaned-up when a channel of type A gets poisoned. In the object Message a number of more specific implicit messages are defined, but in case you define your own class embedding resources, it is your own responsibility to define an implicit object implementing the abstract class Message in which you customize the clean-up.
Defines an implicit Message[A] for any type A <: AnyVal for which there is no implicit in scope defined as implicit def bMessage[A <: B]: Message[A]
PureMessage classes of type AnyVal are not supposed to carry resources, that require customized cleanup, still bear in mind the remark made at def anyRefMessage in case you would make your custom Val types.