From 4b73c7a1ba7cabfc99df7065f90d220b035a4aaf Mon Sep 17 00:00:00 2001
From: Daniel Urban <urban.dani@gmail.com>
Date: Tue, 29 Nov 2022 00:59:33 +0100
Subject: [PATCH] Fix #3283: make Deferred#complete uncancelable

---
 .../main/scala/cats/effect/kernel/Deferred.scala  |  2 +-
 .../scala/cats/effect/kernel/DeferredSpec.scala   | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/kernel/shared/src/main/scala/cats/effect/kernel/Deferred.scala b/kernel/shared/src/main/scala/cats/effect/kernel/Deferred.scala
index bf015fd676..4357ef3755 100644
--- a/kernel/shared/src/main/scala/cats/effect/kernel/Deferred.scala
+++ b/kernel/shared/src/main/scala/cats/effect/kernel/Deferred.scala
@@ -186,7 +186,7 @@ object Deferred {
             }
         }
 
-      F.defer(loop())
+      F.uncancelable(_ => F.defer(loop()))
     }
   }
 
diff --git a/tests/shared/src/test/scala/cats/effect/kernel/DeferredSpec.scala b/tests/shared/src/test/scala/cats/effect/kernel/DeferredSpec.scala
index 581b479e02..2f220a1472 100644
--- a/tests/shared/src/test/scala/cats/effect/kernel/DeferredSpec.scala
+++ b/tests/shared/src/test/scala/cats/effect/kernel/DeferredSpec.scala
@@ -147,5 +147,20 @@ class DeferredSpec extends BaseSpec { outer =>
       }
     }
 
+    "issue #3283: complete must be uncancelable" in real {
+
+      import cats.syntax.all._
+
+      for {
+        d <- Deferred[IO, Int]
+        attemptCompletion = { (n: Int) => d.complete(n).void }
+        res <- List(
+          IO.race(attemptCompletion(1), attemptCompletion(2)).void,
+          d.get.void
+        ).parSequence
+        r <- IO { (res == List((), ())) must beTrue }
+      } yield r
+    }
+
   }
 }