Fix init for Tuple1 case

Author: danicheg

library/src/scala/Tuple.scala

@@ -84,7 +84,7 @@ object Tuple {
 
   /** Type of the initial part of the tuple without its last element */
   type Init[X <: NonEmptyTuple] <: Tuple = X match {
-    case _ *: EmptyTuple => X
+    case _ *: EmptyTuple => EmptyTuple
     case x *: xs =>
       xs match {
         case _ *: EmptyTuple =>

library/src/scala/runtime/Tuples.scala

@@ -375,8 +375,8 @@ object Tuples {
   // Init for Tuple1 to Tuple22
   private def specialCaseInit(self: Tuple): Tuple = {
     (self: Any) match {
-      case self: Tuple1[_] =>
-        self
+      case _: Tuple1[_] =>
+        EmptyTuple
       case self: Tuple2[_, _] =>
         Tuple1(self._1)
       case self: Tuple3[_, _, _] =>

tests/run-deep-subtype/Tuple-init.check

@@ -1,4 +1,4 @@
-(0)
+()
 (0)
 (0,0)
 (0,0,1)
@@ -24,7 +24,7 @@
 (0,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21)
 (0,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22)
 (0,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23)
-(1)
+()
 (1)
 (1,2)
 (1,2,3)
@@ -49,7 +49,7 @@
 (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22)
 (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23)
 (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24)
-(1)
+()
 (1)
 (1,2)
 (1,2,3)