Revert "make 3.2 the default source version"

This reverts commit 969570e.

Author: griggt

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

@@ -51,7 +51,7 @@ 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", "3.2", "future", "3.0-migration", "3.1-migration", "3.2-migration", "future-migration"), "3.2", aliases = List("--source"))
+  val source: Setting[String] = ChoiceSetting("-source", "source version", "source version", List("3.0", "3.1", "3.2", "future", "3.0-migration", "3.1-migration", "3.2-migration", "future-migration"), "3.0", 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

@@ -16,7 +16,7 @@ enum SourceVersion:
   def isAtLeast(v: SourceVersion) = stable.ordinal >= v.ordinal
 
 object SourceVersion extends Property.Key[SourceVersion]:
-  def defaultSourceVersion = `3.2`
+  def defaultSourceVersion = `3.0`
 
   val allSourceVersionNames = values.toList.map(_.toString.toTermName)
 end SourceVersion