From 62dc2943ffb5ae07f3f016b2ecb9cca6e1be6333 Mon Sep 17 00:00:00 2001
From: Atif Aziz <code@raboof.com>
Date: Sat, 28 Dec 2024 23:00:40 +0100
Subject: [PATCH] Allow use of C# 13

---
 Directory.Build.props            | 2 +-
 MoreLinq/Experimental/Memoize.cs | 2 +-
 MoreLinq/Lock.cs                 | 8 ++++++++
 3 files changed, 10 insertions(+), 2 deletions(-)
 create mode 100644 MoreLinq/Lock.cs

diff --git a/Directory.Build.props b/Directory.Build.props
index 222a1c0a6..cecc99270 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <LangVersion>12</LangVersion>
+    <LangVersion>13</LangVersion>
     <Nullable>enable</Nullable>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <AnalysisLevel>8.0-all</AnalysisLevel>
diff --git a/MoreLinq/Experimental/Memoize.cs b/MoreLinq/Experimental/Memoize.cs
index 8e6a3c6b5..9e1cfb68b 100644
--- a/MoreLinq/Experimental/Memoize.cs
+++ b/MoreLinq/Experimental/Memoize.cs
@@ -65,7 +65,7 @@ public static IEnumerable<T> Memoize<T>(this IEnumerable<T> source) =>
     sealed class MemoizedEnumerable<T>(IEnumerable<T> sequence) : IEnumerable<T>, IDisposable
     {
         List<T>? cache;
-        readonly object locker = new();
+        readonly Lock locker = new();
         readonly IEnumerable<T> source = sequence ?? throw new ArgumentNullException(nameof(sequence));
         IEnumerator<T>? sourceEnumerator;
         int? errorIndex;
diff --git a/MoreLinq/Lock.cs b/MoreLinq/Lock.cs
new file mode 100644
index 000000000..ce65fc442
--- /dev/null
+++ b/MoreLinq/Lock.cs
@@ -0,0 +1,8 @@
+#if NET9_0_OR_GREATER
+// https://learn.microsoft.com/dotnet/csharp/language-reference/statements/lock#guidelines
+global using Lock = System.Threading.Lock;
+#else
+// For why "System.Object" instead of "object", see:
+// https://github.com/dotnet/runtime/issues/110242
+global using Lock = System.Object;
+#endif