wip

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

@@ -736,7 +736,11 @@ object desugar {
 
         companionDefs(anyRef, applyMeths ::: unapplyMeth :: toStringMeth :: companionMembers)
       }
-      else if (companionMembers.nonEmpty || companionDerived.nonEmpty || isEnum)
+      else if (isEnum)
+        val r = ref(defn.EnumCompanionClass.typeRef)
+        val r2 = appliedTypeTree(r, ref(requiredClass(className).typeRef) :: Nil)
+        companionDefs(r2, companionMembers)
+      else if (companionMembers.nonEmpty || companionDerived.nonEmpty)
         companionDefs(anyRef, companionMembers)
       else if (isValueClass)
         companionDefs(anyRef, Nil)

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

@@ -740,6 +740,7 @@ class Definitions {
 
   @tu lazy val EnumClass: ClassSymbol = requiredClass("scala.reflect.Enum")
     @tu lazy val Enum_ordinal: Symbol = EnumClass.requiredMethod(nme.ordinal)
+  @tu lazy val EnumCompanionClass: ClassSymbol = requiredClass("scala.reflect.EnumCompanion")
 
   @tu lazy val EnumValueSerializationProxyClass: ClassSymbol = requiredClass("scala.runtime.EnumValueSerializationProxy")
     @tu lazy val EnumValueSerializationProxyConstructor: TermSymbol =

library/src/scala/reflect/Enum.scala

@@ -5,3 +5,11 @@ package scala.reflect
 
   /** A number uniquely identifying a case of an enum */
   def ordinal: Int
+
+//@annotation.transparentTrait trait EnumCompanion extends AnyRef
+
+/** A base trait of all Scala enum companion definitions */
+@annotation.transparentTrait trait EnumCompanion[E <: Enum] extends AnyRef:
+
+  def values : Array[E]
+  def valueOf(name : String) : E

tests/init/neg/enum-desugared.scala

@@ -8,7 +8,7 @@ sealed abstract class ErrorMessageID($name: String, _$ordinal: Int)
   def errorNumber: Int = this.ordinal() - 2
 }
 
-object ErrorMessageID {
+object ErrorMessageID extends scala.reflect.EnumCompanion[ErrorMessageID]{
 
   final val LazyErrorId = $new(0, "LazyErrorId")
   final val NoExplanationID = $new(1, "NoExplanationID")

tests/pos/enum-companion-first.scala

@@ -1,9 +1,10 @@
-object Planet:
-  final val G = 6.67300E-11
+final val G = 6.67300E-11
 
 enum Planet(mass: Double, radius: Double) extends Enum[Planet]:
-  def surfaceGravity = Planet.G * mass / (radius * radius)
+  def surfaceGravity = G * mass / (radius * radius)
   def surfaceWeight(otherMass: Double) =  otherMass * surfaceGravity
 
   case Mercury extends Planet(3.303e+23, 2.4397e6)
   case Venus   extends Planet(4.869e+24, 6.0518e6)
+
+val check = summon[Planet.type <:< scala.reflect.EnumCompanion[Planet]]