Update code paths for .NET 7 as base

Author: Sergio0694

src/CommunityToolkit.Common/Deferred/EventDeferral.cs

@@ -4,6 +4,9 @@
 
 using System;
 using System.ComponentModel;
+#if NET8_0_OR_GREATER
+using System.Runtime.CompilerServices;
+#endif
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -16,8 +19,11 @@ namespace CommunityToolkit.Common.Deferred;
 /// </summary>
 public class EventDeferral : IDisposable
 {
-    // TODO: If/when .NET 6 is base, we can upgrade to non-generic version
+#if NET8_0_OR_GREATER
+    private readonly TaskCompletionSource taskCompletionSource = new();
+#else
     private readonly TaskCompletionSource<object?> taskCompletionSource = new();
+#endif
 
     internal EventDeferral()
     {
@@ -26,7 +32,14 @@ internal EventDeferral()
     /// <summary>
     /// Call when finished with the Deferral.
     /// </summary>
-    public void Complete() => this.taskCompletionSource.TrySetResult(null);
+    public void Complete()
+    {
+#if NET8_0_OR_GREATER
+        this.taskCompletionSource.TrySetResult();
+#else
+        this.taskCompletionSource.TrySetResult(null);
+#endif
+    }
 
     /// <summary>
     /// Waits for the <see cref="EventDeferral"/> to be completed by the event handler.
@@ -38,9 +51,19 @@ internal EventDeferral()
     [Obsolete("This is an internal only method to be used by EventHandler extension classes, public callers should call GetDeferral() instead on the DeferredEventArgs.")]
     public async Task WaitForCompletion(CancellationToken cancellationToken)
     {
-        using (cancellationToken.Register(() => this.taskCompletionSource.TrySetCanceled()))
+        using (cancellationToken.Register(
+#if NET8_0_OR_GREATER
+            callback: static obj => Unsafe.As<EventDeferral>(obj!).taskCompletionSource.TrySetCanceled(),
+#else
+            callback: static obj => ((EventDeferral)obj).taskCompletionSource.TrySetCanceled(),
+#endif
+            state: this))
         {
+#if NET8_0_OR_GREATER
+            await this.taskCompletionSource.Task;
+#else
             _ = await this.taskCompletionSource.Task;
+#endif
         }
     }
 

tests/CommunityToolkit.Mvvm.UnitTests/Test_ObservablePropertyAttribute.cs

@@ -709,12 +709,8 @@ public void Test_ObservableProperty_NullabilityAnnotations_Complex()
         NullabilityInfo rightInfo2 = rightInnerInfo.GenericTypeArguments[2];
 
         Assert.AreEqual(typeof(object), rightInfo2.Type);
-        //Assert.AreEqual(NullabilityState.NotNull, rightInfo2.ReadState);
-        //Assert.AreEqual(NullabilityState.NotNull, rightInfo2.WriteState);
-
-        // The commented out lines are to work around a bug in the NullabilityInfo API in .NET 6.
-        // This has been fixed for .NET 7: https://github.com/dotnet/runtime/pull/63556. The test
-        // cases above can be uncommented when the .NET 7 target (or a more recent version) is added.
+        Assert.AreEqual(NullabilityState.NotNull, rightInfo2.ReadState);
+        Assert.AreEqual(NullabilityState.NotNull, rightInfo2.WriteState);
     }
 #endif