Support the compilation of Scala 2.13 scala.reflect.package

Author: nicolasstucki

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

@@ -670,6 +670,8 @@ class Definitions {
   @tu lazy val ClassTagClass: ClassSymbol = requiredClass("scala.reflect.ClassTag")
   @tu lazy val ClassTagModule: Symbol = ClassTagClass.companionModule
     @tu lazy val ClassTagModule_apply: Symbol = ClassTagModule.requiredMethod(nme.apply)
+  @tu lazy val ReflectPackageClass: Symbol = requiredPackage("scala.reflect.package").moduleClass
+
 
   @tu lazy val QuotedExprClass: ClassSymbol = requiredClass("scala.quoted.Expr")
   @tu lazy val QuotedExprModule: Symbol = QuotedExprClass.companionModule

compiler/src/dotty/tools/dotc/transform/PostTyper.scala

@@ -148,7 +148,11 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
           checkInferredWellFormed(tree.tpt)
           val sym = tree.symbol
           if sym.isScala2Macro && !ctx.settings.XignoreScala2Macros.value then
-            if !sym.owner.unforcedDecls.exists(p => !p.isScala2Macro && p.name == sym.name && p.signature == sym.signature) then
+            if !sym.owner.unforcedDecls.exists(p => !p.isScala2Macro && p.name == sym.name && p.signature == sym.signature)
+               // Allow scala.reflect.materializeClassTag to be able to compile scala/reflect/package.scala
+               // This should be removed on Scala 3.1
+               && sym.owner != defn.ReflectPackageClass
+            then
               report.error("No Scala 3 implementation found for this Scala 2 macro.", tree.sourcePos)
         case _ =>
       processMemberDef(tree)