From 995d63b140f1078a7c853d92d8fce2138c474c1e Mon Sep 17 00:00:00 2001
From: Eugene Flesselle <eugene@flesselle.net>
Date: Tue, 30 Jul 2024 14:27:50 +0200
Subject: [PATCH] Combine cases of `Tuple.Zip` disjoint from `(h1 *: t1, h2 *:
t2)`
If we reach the second case of `Zip[T1 <: Tuple, T2 <: Tuple]`,
then we know `(T1, T2)` is disjoint from `(NonEmptyTuple, NonEmptyTuple)`,
from which we can conclude at least one of the two is an `EmptyTuple`.
Addressing #19175
---
library/src/scala/Tuple.scala | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/library/src/scala/Tuple.scala b/library/src/scala/Tuple.scala
index 8074fe3664e5..8291e17a5cfc 100644
--- a/library/src/scala/Tuple.scala
+++ b/library/src/scala/Tuple.scala
@@ -175,15 +175,12 @@ object Tuple {
}
/** Given two tuples, `A1 *: ... *: An * At` and `B1 *: ... *: Bn *: Bt`
- * where at least one of `At` or `Bt` is `EmptyTuple` or `Tuple`,
- * returns the tuple type `(A1, B1) *: ... *: (An, Bn) *: Ct`
- * where `Ct` is `EmptyTuple` if `At` or `Bt` is `EmptyTuple`, otherwise `Ct` is `Tuple`.
+ * where at least one of `At` or `Bt` is `EmptyTuple`,
+ * returns the tuple type `(A1, B1) *: ... *: (An, Bn) *: EmptyTuple`.
*/
type Zip[T1 <: Tuple, T2 <: Tuple] <: Tuple = (T1, T2) match {
case (h1 *: t1, h2 *: t2) => (h1, h2) *: Zip[t1, t2]
- case (EmptyTuple, _) => EmptyTuple
- case (_, EmptyTuple) => EmptyTuple
- case _ => Tuple
+ case _ => EmptyTuple
}
/** Converts a tuple `(F[T1], ..., F[Tn])` to `(T1, ... Tn)` */