Future of Explicit Null

MarkCLewis · February 11, 2021, 9:29pm

It is possible this question belongs in the Contributors board, but I expect that it will be seen here and I didn’t want to clutter that space.

The Explicit Null feature in Scala 3 is currently enabled by compiler flags. I can’t find any discussion in the documentation or these boards about whether that is expected to be the situation long-term or if explicit nulls will become the default in something like Scala 3.1. I feel like I read that the current plan is to make it the default in the future, but I want to verify. I ask because I am trying to decide if the next edition of my textbooks and videos should assume explicit nulls or not. I don’t want all of my code to immediately become out of date with Scala 3.1.

bjornregnell · February 12, 2021, 9:48am

I have the same problem with my course material and I’m struggling with the same exact question, so thanks for starting this thread! I have tried to read up on this in the different forums, but couldn’t find a good summary of the current general roadmap of deprecation.

It would be really good if there was a 3.1-doc page with what old/new stuff is to be the norm/preference/deprecated/removed by then. My next course instance starts after summer, but my work on course material development needs to take place this spring…

bjornregnell · February 12, 2021, 9:54am

Previously there was a compiler setting that explicitly set the compiler only to accept 3.1 stuff, but this has apparently changed to “future”:

All current compiler settings are available here (code is king ):

github.com

lampepfl/dotty/blob/master/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

package dotty.tools.dotc
package config

import dotty.tools.dotc.core.Contexts._
import dotty.tools.io.{ Directory, PlainDirectory, AbstractFile, JDK9Reflectors }
import PathResolver.Defaults
import rewrites.Rewrites
import Settings.Setting

/** Settings shared by compiler and scaladoc */
trait CommonScalaSettings { self: Settings.SettingGroup =>
  protected def defaultClasspath: String = sys.env.getOrElse("CLASSPATH", ".")

  /** Path related settings */
  val bootclasspath: Setting[String] = PathSetting("-bootclasspath", "Override location of bootstrap class files.", Defaults.scalaBootClassPath, aliases = List("--boot-class-path"))
  val extdirs: Setting[String] = PathSetting("-extdirs", "Override location of installed extensions.", Defaults.scalaExtDirs, aliases = List("--extension-directories"))
  val javabootclasspath: Setting[String] = PathSetting("-javabootclasspath", "Override java boot classpath.", Defaults.javaBootClassPath, aliases = List("--java-boot-class-path"))
  val javaextdirs: Setting[String] = PathSetting("-javaextdirs", "Override java extdirs classpath.", Defaults.javaExtDirs, aliases = List("--java-extension-directories"))
  val sourcepath: Setting[String] = PathSetting("-sourcepath", "Specify location(s) of source files.", Defaults.scalaSourcePath, aliases = List("--source-path"))
  val sourceroot: Setting[String] = PathSetting("-sourceroot", "Specify workspace root directory.", ".")

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