Keep old scheme if option -language:Scala2 is set.

Author: odersky

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -430,6 +430,8 @@ object desugar {
     // new C[Ts](paramss)
     lazy val creatorExpr = New(classTypeRef, constrVparamss nestedMap refOfDef)
 
+    val copiedAccessFlags = if (ctx.scala2Setting) EmptyFlags else AccessFlags
+
     // Methods to add to a case class C[..](p1: T1, ..., pN: Tn)(moreParams)
     //     def _1: T1 = this.p1
     //     ...
@@ -469,7 +471,7 @@ object desugar {
           val copyRestParamss = derivedVparamss.tail.nestedMap(vparam =>
             cpy.ValDef(vparam)(rhs = EmptyTree))
           DefDef(nme.copy, derivedTparams, copyFirstParams :: copyRestParamss, TypeTree(), creatorExpr)
-            .withFlags(Synthetic | constr1.mods.flags & AccessFlags) :: Nil
+            .withFlags(Synthetic | constr1.mods.flags & copiedAccessFlags) :: Nil
         }
       }
 
@@ -574,7 +576,7 @@ object desugar {
           if (mods is Abstract) Nil
           else
             DefDef(nme.apply, derivedTparams, derivedVparamss, applyResultTpt, widenedCreatorExpr)
-              .withFlags(Synthetic | constr1.mods.flags & (DefaultParameterized | AccessFlags)) :: widenDefs
+              .withFlags(Synthetic | constr1.mods.flags & (DefaultParameterized | copiedAccessFlags)) :: widenDefs
         val unapplyMeth = {
           val unapplyParam = makeSyntheticParameter(tpt = classTypeRef)
           val unapplyRHS = if (arity == 0) Literal(Constant(true)) else Ident(unapplyParam.name)

compiler/src/dotty/tools/dotc/core/TypeOps.scala

@@ -327,6 +327,11 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
     }
     scala2Mode
   }
+
+  /** Is option -language:Scala2 set?
+   *  This test is used when we are too early in the pipeline to consider imports.
+   */
+  def scala2Setting = ctx.settings.language.value.contains(nme.Scala2.toString)
 }
 
 object TypeOps {

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

@@ -242,7 +242,7 @@ object Scanners {
 
 // Scala 2 compatibility
 
-    val isScala2Mode: Boolean = ctx.settings.language.value.contains(nme.Scala2.toString)
+    val isScala2Mode: Boolean = ctx.scala2Setting
 
     /** Cannot use ctx.featureEnabled because accessing the context would force too much */
     def testScala2Mode(msg: String, pos: Position = Position(offset)): Boolean = {