From e63145a78f0e00ff6428a7abb8489ba3f5a800cc Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Tue, 20 Feb 2024 11:36:21 +1100
Subject: [PATCH] .

---
 src/Polyfill/Polyfill.targets        | 25 ++++++++++++++-----------
 src/Polyfill/Polyfill_IEnumerable.cs |  4 ++--
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/src/Polyfill/Polyfill.targets b/src/Polyfill/Polyfill.targets
index f456d5f7..cc3ac85d 100644
--- a/src/Polyfill/Polyfill.targets
+++ b/src/Polyfill/Polyfill.targets
@@ -56,17 +56,20 @@
     </PropertyGroup>
     <PropertyGroup>
       <DefineConstants Condition="$(MemoryReferenced)">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="$(LowerFramework.StartsWith('net9'))">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="$(LowerFramework.StartsWith('net8'))">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="$(LowerFramework.StartsWith('net7'))">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="$(LowerFramework.StartsWith('net6'))">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="$(LowerFramework.StartsWith('net5'))">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp3.1'">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp3.0'">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp2.2'">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp2.1'">$(DefineConstants);HAS_SPAN</DefineConstants>
-      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp2.0'">$(DefineConstants)</DefineConstants>
-      <DefineConstants Condition="$(LowerFramework.StartsWith('net4'))">$(DefineConstants)</DefineConstants>
+      <DefineConstants Condition="$(ValueTupleReferenced)">$(DefineConstants);HasValueTuple</DefineConstants>
+      <DefineConstants Condition="$(LowerFramework.StartsWith('net9'))">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="$(LowerFramework.StartsWith('net8'))">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="$(LowerFramework.StartsWith('net7'))">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="$(LowerFramework.StartsWith('net6'))">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="$(LowerFramework.StartsWith('net5'))">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp3.1'">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp3.0'">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp2.2'">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp2.1'">$(DefineConstants);HAS_SPAN;HasValueTuple</DefineConstants>
+      <DefineConstants Condition="'$(LowerFramework)'=='netcoreapp2.0'">$(DefineConstants);HasValueTuple</DefineConstants>
+      <DefineConstants Condition="$(LowerFramework.StartsWith('net47'))">$(DefineConstants);HasValueTuple</DefineConstants>
+      <DefineConstants Condition="$(LowerFramework.StartsWith('net48'))">$(DefineConstants);HasValueTuple</DefineConstants>
+      <DefineConstants Condition="$(LowerFramework.StartsWith('netstandard2'))">$(DefineConstants);HasValueTuple</DefineConstants>
     </PropertyGroup>
   </Target>
   <ItemGroup>
diff --git a/src/Polyfill/Polyfill_IEnumerable.cs b/src/Polyfill/Polyfill_IEnumerable.cs
index e20203c9..4612bc94 100644
--- a/src/Polyfill/Polyfill_IEnumerable.cs
+++ b/src/Polyfill/Polyfill_IEnumerable.cs
@@ -74,10 +74,10 @@ public static IEnumerable<TSource> Except<TSource>(
         params TSource[] items) =>
         target.Except((IEnumerable<TSource>)items, comparer);
 
-#if !NET9_0_OR_GREATER
+#if !NET9_0_OR_GREATER && HasValueTuple
 
     /// <summary>
-    /// TODO
+    /// https://learn.microsoft.com/en-us/dotnet/core/whats-new/dotnet-9/overview#linq
     /// </summary>
     [Link("https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.index#system-linq-enumerable-index-1(system-collections-generic-ienumerable((-0)))")]
     public static IEnumerable<(int Index, TSource Item)> Index<TSource> (this IEnumerable<TSource> source)