Code cleanup.

src/Movere/Common/MaybeNullWhenFalseAttribute.cs

@@ -0,0 +1,7 @@
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false)]
+    internal sealed class MaybeNullWhenFalseAttribute : Attribute
+    {
+    }
+}

src/Movere/Common/StackExtensions.cs

@@ -1,20 +1,20 @@
 #if NETSTANDARD2_0
 
+using System.Runtime.CompilerServices;
+
 namespace System.Collections.Generic
 {
     internal static class StackExtensions
     {
-        public static bool TryPop<T>(this Stack<T> stack, out T result)
+        public static bool TryPop<T>(this Stack<T> stack, [MaybeNullWhenFalse] out T result)
         {
             if (stack.Count > 0)
             {
                 result = stack.Pop();
                 return true;
             }
 
-#pragma warning disable CS8653 // A default expression introduces a null value for a type parameter.
-            result = default;
-#pragma warning restore CS8653 // A default expression introduces a null value for a type parameter.
+            result = default!;
             return false;
         }
     }

src/Movere/ViewModels/FileExplorerTreeViewModel.cs

@@ -21,9 +21,9 @@ public FileExplorerTreeViewModel()
 
             FolderHierarchy = _drives.Select(d => new Folder(d.RootDirectory));
 
-#pragma warning disable CS8619 // Nullability of reference types in value doesn't match target type.
-            SelectedFolderChanged = this.WhenAnyValue(vm => vm.SelectedFolder).Where(folder => folder != null);
-#pragma warning restore CS8619 // Nullability of reference types in value doesn't match target type.
+            SelectedFolderChanged = from folder in this.WhenAnyValue(vm => vm.SelectedFolder)
+                                    where folder != null
+                                    select folder;
         }
 
         public IEnumerable<Folder> FolderHierarchy { get; }