Make EmptyTuple a Product

Author: nicolasstucki

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

@@ -1397,7 +1397,7 @@ class Definitions {
       .updated(AnyValClass, ObjectClass)
       .updated(SingletonClass, ObjectClass)
       .updated(TupleClass, ObjectClass)
-      .updated(EmptyTupleClass, ObjectClass)
+      .updated(EmptyTupleClass, ProductClass)
       .updated(NonEmptyTupleClass, ProductClass)
 
   // ----- Initialization ---------------------------------------------------

library/src-bootstrapped/scala/Tuple.scala

@@ -192,7 +192,7 @@ object Tuple {
 }
 
 /** Tuple of arity zero */
-sealed trait EmptyTuple extends Tuple
+sealed trait EmptyTuple extends Tuple with Product
 
 /** Tuple of arbitrary non-zero arity */
 sealed trait NonEmptyTuple extends Tuple with Product {

library/src-bootstrapped/scala/runtime/Tuple0.scala

@@ -2,6 +2,6 @@ package scala.runtime
 
 /** A tuple of 0 elements; the canonical representation of a [[scala.Product0]].
  */
-/*case*/ object Tuple0 /*extends Product0 */ {
+case object Tuple0 extends Product0 {
  override def toString(): String = "()"
 }