introduce infrastructure for 3.2 language features

compiler/src/dotty/tools/dotc/config/Feature.scala

@@ -76,7 +76,7 @@ object Feature:
   def scala2ExperimentalMacroEnabled(using Context) = enabled(scala2macros)
 
   def sourceVersionSetting(using Context): SourceVersion =
-    SourceVersion.valueOf(ctx.settings.source.value)
+    SourceVersion.lookupSourceVersion.fromSetting(ctx.settings.source.value)
 
   def sourceVersion(using Context): SourceVersion =
     ctx.compilationUnit.sourceVersion match
@@ -85,14 +85,11 @@ object Feature:
 
   def migrateTo3(using Context): Boolean = sourceVersion == `3.0-migration`
 
-  /** If current source migrates to `version`, issue given warning message
+  /** If current source migrates to a version in the series denoted by `version`, issue given warning message
    *  and return `true`, otherwise return `false`.
    */
-  def warnOnMigration(msg: Message, pos: SrcPos,
-      version: SourceVersion)(using Context): Boolean =
-    if sourceVersion.isMigrating && sourceVersion.stable == version
-       || (version == `3.0` || version == `3.1` || version == `3.2`) && migrateTo3
-    then
+  def warnOnMigration(msg: Message, pos: SrcPos, version: SourceVersion)(using Context): Boolean =
+    if sourceVersion.isMigrating && sourceVersion.series == version.series then
       report.migrationWarning(msg, pos)
       true
     else

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -5,6 +5,7 @@ import scala.language.unsafeNulls
 
 import dotty.tools.dotc.config.PathResolver.Defaults
 import dotty.tools.dotc.config.Settings.{Setting, SettingGroup}
+import dotty.tools.dotc.config.SourceVersion
 import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.rewrites.Rewrites
 import dotty.tools.io.{AbstractFile, Directory, JDK9Reflectors, PlainDirectory}
@@ -51,7 +52,15 @@ trait AllScalaSettings extends CommonScalaSettings, PluginSettings, VerboseSetti
   /* Path related settings */
   val semanticdbTarget: Setting[String] = PathSetting("-semanticdb-target", "Specify an alternative output directory for SemanticDB files.", "")
 
-  val source: Setting[String] = ChoiceSetting("-source", "source version", "source version", List("3.0", "3.1", "future", "3.0-migration", "future-migration"), "3.0", aliases = List("--source"))
+  private val SourceVersionOptions =
+    SourceVersion
+      .lookupSourceVersion.fromSetting
+      .toList
+      // we want `3.1-migration` to be before `3.1`, but both map to same SourceVersion
+      .sortBy((key, version) => (version.ordinal, !key.endsWith("-migration")))
+      .map((key, _) => key)
+
+  val source: Setting[String] = ChoiceSetting("-source", "source version", "source version", SourceVersionOptions, SourceVersion.defaultSourceVersion.toString, aliases = List("--source"))
   val uniqid: Setting[Boolean] = BooleanSetting("-uniqid", "Uniquely tag all identifiers in debugging output.", aliases = List("--unique-id"))
   val rewrite: Setting[Option[Rewrites]] = OptionSetting[Rewrites]("-rewrite", "When used in conjunction with a `...-migration` source version, rewrites sources to migrate to new version.", aliases = List("--rewrite"))
   val fromTasty: Setting[Boolean] = BooleanSetting("-from-tasty", "Compile classes from tasty files. The arguments are .tasty or .jar files.", aliases = List("--from-tasty"))

compiler/src/dotty/tools/dotc/config/SourceVersion.scala

@@ -5,17 +5,60 @@ package config
 import core.Decorators.*
 import util.Property
 
+import scala.annotation.threadUnsafe
+import dotty.tools.dotc.core.Names.Name
+
+/** Enum expressing series of source versions,
+ *  where each series begins by a migration version, followed by a series of stable versions.
+ *  e.g. `3.0-migration`, `3.0`, `3.1` make one series, `3.0`, as they describe the same semantics.
+ *  `future-migration`, then begins the another series of stable versions, `future`, because in this version we
+ *  enable more features.
+ *
+ *  @note This enum does not need to correspond to the scala.language imports. E.g. if a user imports
+ *  `scala.language.3.1-migration`, the SourceVersion will be set to `3.1` (see `lookupSourceVersion`).
+ *
+ */
 enum SourceVersion:
-  case `3.0-migration`, `3.0`, `3.1`, `3.2`, `future-migration`, `future`
+  case `3.0-migration`, `3.0`, `3.1` // Note: do not add `3.1-migration` here, 3.1 is the same language as 3.0.
+  case `3.2`, `3.2-migration` // !!! DELETE `3.2-migration` BEFORE RELEASING 3.2.0 if we do not enable features from `future`
+  case `future-migration`, `future`
 
   val isMigrating: Boolean = toString.endsWith("-migration")
 
-  def stable: SourceVersion =
-    if isMigrating then SourceVersion.values(ordinal + 1) else this
+  private inline def nextVersion: SourceVersion = SourceVersion.fromOrdinal(ordinal + 1)
+  private inline def previousVersion: SourceVersion = SourceVersion.fromOrdinal(ordinal - 1)
+
+  @threadUnsafe lazy val series: SourceVersion =
+    if isMigrating then nextVersion else previousVersion.series
 
-  def isAtLeast(v: SourceVersion) = stable.ordinal >= v.ordinal
+  def isAtLeast(v: SourceVersion) = this.series.ordinal >= v.series.ordinal
 
 object SourceVersion extends Property.Key[SourceVersion]:
+  def defaultSourceVersion = `3.2`
+
+  object lookupSourceVersion:
+
+    /** A map from with keys matching the `scala.language` imports,
+     *  and values being the corresponding `SourceVersion`, or the next
+     *  stable version if the key ends with `-migration` and no matching SourceVersion exists.
+     */
+    val fromSetting: Map[String, SourceVersion] =
+      val (migratingVersions, stableVersions) = values.partition(_.isMigrating)
+      val entries = stableVersions.flatMap(stable =>
+        val migratingKey = s"${stable}-migration"
+        val migratingEntry =
+          migratingVersions.find(_.toString == migratingKey) match
+            case Some(migrating) => migratingKey -> migrating
+            case _               => migratingKey -> stable
+        val stableEntry = stable.toString -> stable
+        stableEntry :: migratingEntry :: Nil
+      )
+      Map.from(entries)
+
+    /** An immutable array with keys matching the `scala.language` imports
+     *  corresponding to source versions
+     */
+    val fromImport: IArray[Name] =
+      IArray.from(fromSetting.iterator.map((key, _) => key.toTermName))
 
-  val allSourceVersionNames = values.toList.map(_.toString.toTermName)
 end SourceVersion

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -3140,14 +3140,14 @@ object Parsers {
           in.languageImportContext = in.languageImportContext.importContext(imp, NoSymbol)
           for
             case ImportSelector(id @ Ident(imported), EmptyTree, _) <- selectors
-            if allSourceVersionNames.contains(imported)
+            if lookupSourceVersion.fromImport.contains(imported)
           do
             if !outermost then
               syntaxError(i"source version import is only allowed at the toplevel", id.span)
             else if ctx.compilationUnit.sourceVersion.isDefined then
               syntaxError(i"duplicate source version import", id.span)
             else
-              ctx.compilationUnit.sourceVersion = Some(SourceVersion.valueOf(imported.toString))
+              ctx.compilationUnit.sourceVersion = Some(lookupSourceVersion.fromSetting(imported.toString))
         case None =>
       imp
 

compiler/src/dotty/tools/dotc/report.scala

@@ -67,10 +67,9 @@ object report:
     error(ex.toMessage, pos, sticky = true)
     if ctx.settings.YdebugTypeError.value then ex.printStackTrace()
 
-  def errorOrMigrationWarning(msg: Message, pos: SrcPos = NoSourcePosition,
-      from: SourceVersion)(using Context): Unit =
+  def errorOrMigrationWarning(msg: Message, pos: SrcPos = NoSourcePosition, from: SourceVersion)(using Context): Unit =
     if sourceVersion.isAtLeast(from) then
-      if sourceVersion.isMigrating && sourceVersion.ordinal <= from.ordinal then migrationWarning(msg, pos)
+      if sourceVersion.isMigrating && sourceVersion.series == from.series then migrationWarning(msg, pos)
       else error(msg, pos)
 
   def restrictionError(msg: Message, pos: SrcPos = NoSourcePosition)(using Context): Unit =

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -38,7 +38,7 @@ class CompilationTests {
       compileFilesInDir("tests/pos-special/spec-t5545", defaultOptions),
       compileFilesInDir("tests/pos-special/strawman-collections", allowDeepSubtypes),
       compileFilesInDir("tests/pos-special/isInstanceOf", allowDeepSubtypes.and("-Xfatal-warnings")),
-      compileFilesInDir("tests/new", defaultOptions.and("-source", "3.1")), // just to see whether 3.1 works
+      compileFilesInDir("tests/new", defaultOptions.and("-source", "3.2")), // just to see whether 3.2 works
       compileFilesInDir("tests/pos-scala2", scala2CompatMode),
       compileFilesInDir("tests/pos-custom-args/erased", defaultOptions.and("-language:experimental.erasedDefinitions")),
       compileFilesInDir("tests/pos", defaultOptions.and("-Ysafe-init")),

compiler/test/dotty/tools/dotc/config/SourceVersionTest.scala

@@ -0,0 +1,98 @@
+package dotty.tools.dotc.config
+
+import dotty.tools.dotc.core.Decorators.*
+
+import org.junit.Test
+import org.junit.Assert.*
+
+import SourceVersionTest.*
+
+class SourceVersionTest:
+
+  @Test def `importedVersion`: Unit =
+    assertEquals(SourceVersion.`3.0-migration`, importLanguageDot("3.0-migration"))
+    assertEquals(SourceVersion.`3.0`, importLanguageDot("3.0"))
+
+    // crucial that here `import scala.language.3.1-migration` sets the source version to `3.1`
+    assertEquals(SourceVersion.`3.1`, importLanguageDot("3.1-migration"))
+
+    assertEquals(SourceVersion.`3.1`, importLanguageDot("3.1"))
+    assertEquals(SourceVersion.`3.2-migration`, importLanguageDot("3.2-migration"))
+    assertEquals(SourceVersion.`3.2`, importLanguageDot("3.2"))
+    assertEquals(SourceVersion.`future-migration`, importLanguageDot("future-migration"))
+    assertEquals(SourceVersion.`future`, importLanguageDot("future"))
+
+  @Test def `series`: Unit =
+    assertEquals(SourceVersion.`3.0`, SourceVersion.`3.0-migration`.series)
+    assertEquals(SourceVersion.`3.0`, SourceVersion.`3.0`.series)
+    assertEquals(SourceVersion.`3.0`, SourceVersion.`3.1`.series)
+    assertEquals(SourceVersion.`3.2`, SourceVersion.`3.2-migration`.series)
+    assertEquals(SourceVersion.`3.2`, SourceVersion.`3.2`.series)
+    assertEquals(SourceVersion.`future`, SourceVersion.`future-migration`.series)
+    assertEquals(SourceVersion.`future`, SourceVersion.`future`.series)
+
+  @Test def `isAtLeast 3.0`: Unit =
+    // trues
+    assertTrue(SourceVersion.`3.1`.isAtLeast(SourceVersion.`3.1`))
+    assertTrue(SourceVersion.`3.1`.isAtLeast(SourceVersion.`3.0`))
+    assertTrue(SourceVersion.`3.1`.isAtLeast(SourceVersion.`3.0-migration`))
+    assertTrue(SourceVersion.`3.0`.isAtLeast(SourceVersion.`3.1`))
+    assertTrue(SourceVersion.`3.0`.isAtLeast(SourceVersion.`3.0`))
+    assertTrue(SourceVersion.`3.0`.isAtLeast(SourceVersion.`3.0-migration`))
+    assertTrue(SourceVersion.`3.0-migration`.isAtLeast(SourceVersion.`3.1`))
+    assertTrue(SourceVersion.`3.0-migration`.isAtLeast(SourceVersion.`3.0`))
+    assertTrue(SourceVersion.`3.0-migration`.isAtLeast(SourceVersion.`3.0-migration`))
+    // falses
+    assertFalse(SourceVersion.`3.0-migration`.isAtLeast(SourceVersion.`future`))
+    assertFalse(SourceVersion.`3.0-migration`.isAtLeast(SourceVersion.`future-migration`))
+    assertFalse(SourceVersion.`3.0-migration`.isAtLeast(SourceVersion.`3.2`))
+    assertFalse(SourceVersion.`3.0-migration`.isAtLeast(SourceVersion.`3.2-migration`))
+    assertFalse(SourceVersion.`3.0`.isAtLeast(SourceVersion.`future`))
+    assertFalse(SourceVersion.`3.0`.isAtLeast(SourceVersion.`future-migration`))
+    assertFalse(SourceVersion.`3.0`.isAtLeast(SourceVersion.`3.2`))
+    assertFalse(SourceVersion.`3.0`.isAtLeast(SourceVersion.`3.2-migration`))
+    assertFalse(SourceVersion.`3.1`.isAtLeast(SourceVersion.`future`))
+    assertFalse(SourceVersion.`3.1`.isAtLeast(SourceVersion.`future-migration`))
+    assertFalse(SourceVersion.`3.1`.isAtLeast(SourceVersion.`3.2`))
+    assertFalse(SourceVersion.`3.1`.isAtLeast(SourceVersion.`3.2-migration`))
+
+  @Test def `isAtLeast 3.2`: Unit =
+    // trues
+    assertTrue(SourceVersion.`3.2`.isAtLeast(SourceVersion.`3.2`))
+    assertTrue(SourceVersion.`3.2`.isAtLeast(SourceVersion.`3.2-migration`))
+    assertTrue(SourceVersion.`3.2`.isAtLeast(SourceVersion.`3.1`))
+    assertTrue(SourceVersion.`3.2`.isAtLeast(SourceVersion.`3.0`))
+    assertTrue(SourceVersion.`3.2`.isAtLeast(SourceVersion.`3.0-migration`))
+    assertTrue(SourceVersion.`3.2-migration`.isAtLeast(SourceVersion.`3.2`))
+    assertTrue(SourceVersion.`3.2-migration`.isAtLeast(SourceVersion.`3.2-migration`))
+    assertTrue(SourceVersion.`3.2-migration`.isAtLeast(SourceVersion.`3.1`))
+    assertTrue(SourceVersion.`3.2-migration`.isAtLeast(SourceVersion.`3.0`))
+    assertTrue(SourceVersion.`3.2-migration`.isAtLeast(SourceVersion.`3.0-migration`))
+    // falses
+    assertFalse(SourceVersion.`3.2-migration`.isAtLeast(SourceVersion.`future`))
+    assertFalse(SourceVersion.`3.2-migration`.isAtLeast(SourceVersion.`future-migration`))
+    assertFalse(SourceVersion.`3.2`.isAtLeast(SourceVersion.`future`))
+    assertFalse(SourceVersion.`3.2`.isAtLeast(SourceVersion.`future-migration`))
+
+  @Test def `isAtLeast future`: Unit =
+    // trues
+    assertTrue(SourceVersion.`future`.isAtLeast(SourceVersion.`future`))
+    assertTrue(SourceVersion.`future`.isAtLeast(SourceVersion.`future-migration`))
+    assertTrue(SourceVersion.`future`.isAtLeast(SourceVersion.`3.2`))
+    assertTrue(SourceVersion.`future`.isAtLeast(SourceVersion.`3.2-migration`))
+    assertTrue(SourceVersion.`future`.isAtLeast(SourceVersion.`3.1`))
+    assertTrue(SourceVersion.`future`.isAtLeast(SourceVersion.`3.0`))
+    assertTrue(SourceVersion.`future`.isAtLeast(SourceVersion.`3.0-migration`))
+    assertTrue(SourceVersion.`future-migration`.isAtLeast(SourceVersion.`future`))
+    assertTrue(SourceVersion.`future-migration`.isAtLeast(SourceVersion.`future-migration`))
+    assertTrue(SourceVersion.`future-migration`.isAtLeast(SourceVersion.`3.2`))
+    assertTrue(SourceVersion.`future-migration`.isAtLeast(SourceVersion.`3.2-migration`))
+    assertTrue(SourceVersion.`future-migration`.isAtLeast(SourceVersion.`3.1`))
+    assertTrue(SourceVersion.`future-migration`.isAtLeast(SourceVersion.`3.0`))
+    assertTrue(SourceVersion.`future-migration`.isAtLeast(SourceVersion.`3.0-migration`))
+    // no falses
+
+object SourceVersionTest:
+
+  def importLanguageDot(feature: String): SourceVersion =
+    SourceVersion.lookupSourceVersion.fromSetting(feature)

library/src/scala/runtime/stdLibPatches/language.scala

@@ -162,19 +162,33 @@ object language:
   @compileTimeOnly("`3.1` can only be used at compile time in import statements")
   object `3.1`
 
-/* This can be added when we go to 3.2
   /** Set source version to 3.2-migration.
     *
-    * @see [[https://scalacenter.github.io/scala-3-migration-guide/docs/scala-3-migration-mode]]
+    * @see [[https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html]]
     */
   @compileTimeOnly("`3.2-migration` can only be used at compile time in import statements")
   object `3.2-migration`
 
   /** Set source version to 3.2
     *
-    * @see [[https://scalacenter.github.io/scala-3-migration-guide/docs/scala-3-migration-mode]]
+    * @see [[https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html]]
     */
   @compileTimeOnly("`3.2` can only be used at compile time in import statements")
   object `3.2`
+
+/* This can be added when we go to 3.3
+  /** Set source version to 3.3-migration.
+    *
+    * @see [[https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html]]
+    */
+  @compileTimeOnly("`3.3-migration` can only be used at compile time in import statements")
+  object `3.3-migration`
+
+  /** Set source version to 3.3
+    *
+    * @see [[https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html]]
+    */
+  @compileTimeOnly("`3.3` can only be used at compile time in import statements")
+  object `3.3`
 */
 end language

tests/pos/source-import-3-2-migration.scala

@@ -0,0 +1 @@
+import language.`3.2-migration`

tests/pos/source-import-3-2.scala

@@ -0,0 +1 @@
+import language.`3.2`