var x: A = _
that was used to indicate an uninitialized field, has been dropped. At its place there is a special value
uninitialized in the
scala.compiletime package. To get an uninitialized field, you now write
import scala.compiletime.uninitialized var x: A = uninitialized
To enable cross-compilation,
_ is still supported, but it will be dropped in a future 3.x version.