From 72c3c66b1dee2515fefe9474bd2248acf8f3ffe5 Mon Sep 17 00:00:00 2001
From: Atif Aziz <code@raboof.com>
Date: Sun, 29 Dec 2024 00:10:14 +0100
Subject: [PATCH] Allow use of C# 13

---
 Directory.Build.props            | 2 +-
 MoreLinq/Experimental/Memoize.cs | 4 +++-
 MoreLinq/Lock.cs                 | 8 ++++++++
 3 files changed, 12 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..40acdd15d 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;
@@ -77,7 +77,9 @@ public IEnumerator<T> GetEnumerator()
             {
                 lock (this.locker)
                 {
+#pragma warning disable CA1508 // Avoid dead conditional code
                     if (this.cache == null)
+#pragma warning restore CA1508 // Avoid dead conditional code
                     {
                         this.error?.Throw();
 
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