This splits DartTypeVisitor(1) into a pure interface and a
DartTypeVisitor(1)DefaultMixin with the base implementation. This is
a step towards avoid having an accidental default implementation where
a static error would have been preferable.
TEST=existing
Change-Id: Ieea9a773a9b70897a2db10cff8d721831a702a8b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/324780
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Jens Johansen <jensj@google.com>
Reviewed-by: Mayank Patke <fishythefish@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Johnni Winther
fefa87d1e6