From 421591fc792480033e28714bb2ecc60c32923d9b Mon Sep 17 00:00:00 2001
From: Flavio Brasil <fwbrasil@gmail.com>
Date: Sat, 11 Mar 2023 14:08:13 -0800
Subject: [PATCH] optimization: avoid NotGiven allocations

---
 library/src/scala/util/NotGiven.scala | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/library/src/scala/util/NotGiven.scala b/library/src/scala/util/NotGiven.scala
index 99cc903d4426..973e709042cb 100644
--- a/library/src/scala/util/NotGiven.scala
+++ b/library/src/scala/util/NotGiven.scala
@@ -31,11 +31,13 @@ trait LowPriorityNotGiven {
 }
 object NotGiven extends LowPriorityNotGiven {
 
+  private val cachedValue = new NotGiven[Nothing]()
+
   /** A value of type `NotGiven` to signal a successful search for `NotGiven[C]` (i.e. a failing
    *  search for `C`). A reference to this value will be explicitly constructed by Dotty's
    *  implicit search algorithm
    */
-  def value: NotGiven[Nothing] = new NotGiven[Nothing]()
+  def value: NotGiven[Nothing] = cachedValue
 
   /** One of two ambiguous methods used to emulate negation in Scala 2 */
   given amb1[T](using ev: T): NotGiven[T] = ???