Add missing cases for Tuple.{Head, Tail, Init, Last}

library/src/scala/Tuple.scala

@@ -98,24 +98,27 @@ object Tuple {
   /** Type of the head of a tuple */
   type Head[X <: Tuple] = X match {
     case x *: _ => x
+    case EmptyTuple => Nothing
   }
 
   /** Type of the initial part of the tuple without its last element */
   type Init[X <: Tuple] <: Tuple = X match {
     case _ *: EmptyTuple => EmptyTuple
-    case x *: xs =>
-      x *: Init[xs]
+    case x *: xs => x *: Init[xs]
+    case EmptyTuple => Nothing
   }
 
   /** Type of the tail of a tuple */
   type Tail[X <: Tuple] <: Tuple = X match {
     case _ *: xs => xs
+    case EmptyTuple => Nothing
   }
 
   /** Type of the last element of a tuple */
   type Last[X <: Tuple] = X match {
     case x *: EmptyTuple => x
     case _ *: xs => Last[xs]
+    case EmptyTuple => Nothing
   }
 
   /** Type of the concatenation of two tuples */

tests/pos/tupleMatchTypes.scala

@@ -0,0 +1,36 @@
+import scala.Tuple.*
+
+type T1; type T2; type T3; type T4; type T5; type T6; type T7; type T8; type T9; type T10; type T11; type T12; type T13; type T14; type T15; type T16; type T17; type T18; type T19; type T20; type T21; type T22; type T23;
+
+type Tup0 = EmptyTuple
+type Tup1 = T1 *: EmptyTuple
+type Tup2 = (T1, T2)
+type Tup22 = (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22)
+type Tup23 = (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, T23)
+
+def testHead: Unit =
+  summon[Head[Tup0] =:= Nothing]
+  summon[Head[Tup1] =:= T1]
+  summon[Head[Tup2] =:= T1]
+  summon[Head[Tup22] =:= T1]
+  summon[Head[Tup23] =:= T1]
+
+def testLast: Unit =
+  summon[Last[Tup0] =:= Nothing]
+  summon[Last[Tup1] =:= T1]
+  summon[Last[Tup2] =:= T2]
+  summon[Last[Tup22] =:= T22]
+  summon[Last[Tup23] =:= T23]
+
+def testTail: Unit =
+  summon[Tail[Tup0] =:= Nothing]
+  summon[Tail[Tup1] =:= EmptyTuple]
+  summon[Tail[Tup2] =:= T2 *: EmptyTuple]
+  summon[Tail[Tup22] =:= (T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22)]
+  summon[Tail[Tup23] =:= (T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, T23)]
+
+def testInit: Unit =
+  summon[Init[Tup0] =:= Nothing]
+  summon[Init[Tup1] =:= EmptyTuple]
+  summon[Init[Tup22] =:= (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21)]
+  summon[Init[Tup23] =:= (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22)]