Johnni Winther
01f582df78
This splits visitors for (Tree)Visitor(1) into pure interfaces, mixins, and a base class with the base implementation. This is a step towards avoid having an accidental default implementation where a static error would have been preferable. This extract a ConstantReferenceVisitor(1) and its corresponding DefaultMixin from the Visitor(1) interface. TEST=existing Change-Id: Ibc55bed9cff76581deaade91a10600c17fafc6dd Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/325704 Reviewed-by: Mayank Patke <fishythefish@google.com> Reviewed-by: Ömer Ağacan <omersa@google.com> Commit-Queue: Johnni Winther <johnniwinther@google.com> Reviewed-by: Jens Johansen <jensj@google.com>