From 5f9be08ee4e6af2107763a617e4ff93f16ca4ab5 Mon Sep 17 00:00:00 2001
From: Atif Aziz <code@raboof.com>
Date: Tue, 23 Mar 2021 22:30:55 +0100
Subject: [PATCH] Fix "GroupAdjacent" null key handling bug

---
 MoreLinq.Test/GroupAdjacentTest.cs | 24 ++++++++++++++++++++++++
 MoreLinq/GroupAdjacent.cs          |  4 ++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/MoreLinq.Test/GroupAdjacentTest.cs b/MoreLinq.Test/GroupAdjacentTest.cs
index f8bb13ea9..995405f1d 100644
--- a/MoreLinq.Test/GroupAdjacentTest.cs
+++ b/MoreLinq.Test/GroupAdjacentTest.cs
@@ -198,6 +198,30 @@ public void GroupAdjacentSourceSequenceResultSelectorComparer()
             reader.ReadEnd();
         }
 
+        [Test]
+        public void GroupAdjacentSourceSequenceWithSomeNullKeys()
+        {
+            var groupings =
+                Enumerable.Range(1, 5)
+                          .SelectMany(x => Enumerable.Repeat((int?)x, x).Append(null))
+                          .GroupAdjacent(x => x);
+
+            int?[] aNull = { null };
+
+            using var reader = groupings.Read();
+            AssertGrouping(reader, 1, 1);
+            AssertGrouping(reader, null, aNull);
+            AssertGrouping(reader, 2, 2, 2);
+            AssertGrouping(reader, null, aNull);
+            AssertGrouping(reader, 3, 3, 3, 3);
+            AssertGrouping(reader, null, aNull);
+            AssertGrouping(reader, 4, 4, 4, 4, 4);
+            AssertGrouping(reader, null, aNull);
+            AssertGrouping(reader, 5, 5, 5, 5, 5, 5);
+            AssertGrouping(reader, null, aNull);
+            reader.ReadEnd();
+        }
+
         static void AssertGrouping<TKey, TElement>(SequenceReader<System.Linq.IGrouping<TKey, TElement>> reader,
             TKey key, params TElement[] elements)
         {
diff --git a/MoreLinq/GroupAdjacent.cs b/MoreLinq/GroupAdjacent.cs
index f19eeeb9a..cc57e5167 100644
--- a/MoreLinq/GroupAdjacent.cs
+++ b/MoreLinq/GroupAdjacent.cs
@@ -273,7 +273,7 @@ static IEnumerable<TResult> GroupAdjacentImpl<TSource, TKey, TElement, TResult>(
                 var key = keySelector(iterator.Current);
                 var element = elementSelector(iterator.Current);
 
-                if (group is ({} k, {} members))
+                if (group is (var k, {} members))
                 {
                     if (comparer.Equals(k, key))
                     {
@@ -290,7 +290,7 @@ static IEnumerable<TResult> GroupAdjacentImpl<TSource, TKey, TElement, TResult>(
             }
 
             {
-                if (group is ({} k, {} members))
+                if (group is (var k, {} members))
                     yield return resultSelector(k, members);
             }
         }