Fix nullability warnings

ILSpy/AssemblyList.cs

@@ -72,7 +72,7 @@ namespace ICSharpCode.ILSpy
 		/// Loads an assembly list from XML.
 		/// </summary>
 		public AssemblyList(XElement listElement)
-			: this((string)listElement.Attribute("name"))
+			: this((string?)listElement.Attribute("name") ?? AssemblyListManager.DefaultListName)
 		{
 			foreach (var asm in listElement.Elements("Assembly"))
 			{
@@ -184,7 +184,7 @@ namespace ICSharpCode.ILSpy
 			}
 		}
 
-		void Assemblies_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+		void Assemblies_CollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
 		{
 			Debug.Assert(Monitor.IsEntered(lockObj));
 			if (CollectionChangeHasEffectOnSave(e))
@@ -199,9 +199,9 @@ namespace ICSharpCode.ILSpy
 			switch (e.Action)
 			{
 				case NotifyCollectionChangedAction.Add:
-					return e.NewItems.Cast<LoadedAssembly>().Any(asm => !asm.IsAutoLoaded);
+					return e.NewItems.EmptyIfNull().Cast<LoadedAssembly>().Any(asm => !asm.IsAutoLoaded);
 				case NotifyCollectionChangedAction.Remove:
-					return e.OldItems.Cast<LoadedAssembly>().Any(asm => !asm.IsAutoLoaded);
+					return e.OldItems.EmptyIfNull().Cast<LoadedAssembly>().Any(asm => !asm.IsAutoLoaded);
 				default:
 					return true;
 			}
@@ -283,7 +283,7 @@ namespace ICSharpCode.ILSpy
 		{
 			bool isUIThread = App.Current.Dispatcher.Thread == Thread.CurrentThread;
 
-			LoadedAssembly asm;
+			LoadedAssembly? asm;
 			lock (lockObj)
 			{
 				if (byFilename.TryGetValue(file, out asm))
@@ -319,7 +319,7 @@ namespace ICSharpCode.ILSpy
 			file = Path.GetFullPath(file);
 			lock (lockObj)
 			{
-				if (!byFilename.TryGetValue(file, out LoadedAssembly target))
+				if (!byFilename.TryGetValue(file, out LoadedAssembly? target))
 					return null;
 				int index = this.assemblies.IndexOf(target);
 				if (index < 0)

ILSpy/AssemblyListSnapshot.cs

@@ -56,7 +56,7 @@ namespace ICSharpCode.ILSpy
 				lookup = await CreateLoadedAssemblyLookupAsync(shortNames: isWinRT).ConfigureAwait(false);
 				lookup = LazyInit.GetOrSet(ref isWinRT ? ref asmLookupByShortName : ref asmLookupByFullName, lookup);
 			}
-			if (lookup.TryGetValue(key, out PEFile module))
+			if (lookup.TryGetValue(key, out PEFile? module))
 				return module;
 			return null;
 		}

ILSpy/ExtensionMethods.cs

@@ -16,12 +16,17 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+#nullable enable
+
 using System;
+using System.Collections;
 using System.Collections.Generic;
+using System.Linq;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Media;
 
+using ICSharpCode.Decompiler.Util;
 using ICSharpCode.ILSpy.Options;
 
 namespace ICSharpCode.ILSpy
@@ -38,7 +43,7 @@ namespace ICSharpCode.ILSpy
 					list.Add(item);
 		}
 
-		public static T PeekOrDefault<T>(this Stack<T> stack)
+		public static T? PeekOrDefault<T>(this Stack<T> stack)
 		{
 			if (stack.Count == 0)
 				return default(T);
@@ -118,6 +123,11 @@ namespace ICSharpCode.ILSpy
 			value = pair.Value;
 		}
 
+		internal static IEnumerable<T> EmptyIfNull<T>(this IEnumerable<T>? inst) => inst ?? Enumerable.Empty<T>();
+		internal static IEnumerable EmptyIfNull(this IEnumerable? inst) => inst ?? Enumerable.Empty<object>();
+		internal static IList<T> EmptyIfNull<T>(this IList<T>? inst) => inst ?? EmptyList<T>.Instance;
+		internal static IList EmptyIfNull(this IList? inst) => inst ?? Array.Empty<object>();
+
 		public static string ToSuffixString(this System.Reflection.Metadata.EntityHandle handle)
 		{
 			if (!DisplaySettingsPanel.CurrentDisplaySettings.ShowMetadataTokens)
@@ -218,7 +228,7 @@ namespace ICSharpCode.ILSpy
 		}
 		#endregion
 
-		public static T FindVisualChild<T>(this DependencyObject depObj) where T : DependencyObject
+		public static T? FindVisualChild<T>(this DependencyObject? depObj) where T : DependencyObject
 		{
 			if (depObj != null)
 			{
@@ -230,7 +240,7 @@ namespace ICSharpCode.ILSpy
 						return (T)child;
 					}
 
-					T childItem = FindVisualChild<T>(child);
+					T? childItem = FindVisualChild<T>(child);
 					if (childItem != null)
 						return childItem;
 				}
@@ -238,7 +248,7 @@ namespace ICSharpCode.ILSpy
 			return null;
 		}
 
-		public static T GetParent<T>(this DependencyObject depObj) where T : DependencyObject
+		public static T? GetParent<T>(this DependencyObject? depObj) where T : DependencyObject
 		{
 			if (depObj == null)
 				return null;

ILSpy/LoadedAssembly.cs

@@ -218,7 +218,7 @@ namespace ICSharpCode.ILSpy
 			return LazyInitializer.EnsureInitialized(ref this.typeSystem, () => {
 				var module = GetPEFileOrNull();
 				if (module == null)
-					return null;
+					return null!;
 				return new SimpleCompilation(
 					module.WithOptions(TypeSystemOptions.Default | TypeSystemOptions.Uncached | TypeSystemOptions.KeepModifiers),
 					MinimalCorlib.Instance);
@@ -580,42 +580,44 @@ namespace ICSharpCode.ILSpy
 						return module;
 				}
 
-
-				string file = Path.Combine(Path.GetDirectoryName(mainModule.FileName), moduleName);
-				if (File.Exists(file))
+				string? directory = Path.GetDirectoryName(mainModule.FileName);
+				if (directory != null)
 				{
-					// Load module from disk
-					LoadedAssembly? asm;
-					if (loadOnDemand)
+					string file = Path.Combine(directory, moduleName);
+					if (File.Exists(file))
 					{
-						asm = assemblyList.OpenAssembly(file, isAutoLoaded: true);
-					}
-					else
-					{
-						asm = assemblyList.FindAssembly(file);
-					}
-					if (asm != null)
-					{
-						return await asm.GetPEFileOrNullAsync().ConfigureAwait(false);
+						// Load module from disk
+						LoadedAssembly? asm;
+						if (loadOnDemand)
+						{
+							asm = assemblyList.OpenAssembly(file, isAutoLoaded: true);
+						}
+						else
+						{
+							asm = assemblyList.FindAssembly(file);
+						}
+						if (asm != null)
+						{
+							return await asm.GetPEFileOrNullAsync().ConfigureAwait(false);
+						}
 					}
 				}
-				else
+
+				// Module does not exist on disk, look for one with a matching name in the assemblylist:
+				foreach (LoadedAssembly loaded in alreadyLoadedAssemblies.Assemblies)
 				{
-					// Module does not exist on disk, look for one with a matching name in the assemblylist:
-					foreach (LoadedAssembly loaded in alreadyLoadedAssemblies.Assemblies)
+					var module = await loaded.GetPEFileOrNullAsync().ConfigureAwait(false);
+					var reader = module?.Metadata;
+					if (reader == null || reader.IsAssembly)
+						continue;
+					var moduleDef = reader.GetModuleDefinition();
+					if (moduleName.Equals(reader.GetString(moduleDef.Name), StringComparison.OrdinalIgnoreCase))
 					{
-						var module = await loaded.GetPEFileOrNullAsync().ConfigureAwait(false);
-						var reader = module?.Metadata;
-						if (reader == null || reader.IsAssembly)
-							continue;
-						var moduleDef = reader.GetModuleDefinition();
-						if (moduleName.Equals(reader.GetString(moduleDef.Name), StringComparison.OrdinalIgnoreCase))
-						{
-							referenceLoadInfo.AddMessageOnce(moduleName, MessageKind.Info, "Success - Found in Assembly List");
-							return module;
-						}
+						referenceLoadInfo.AddMessageOnce(moduleName, MessageKind.Info, "Success - Found in Assembly List");
+						return module;
 					}
 				}
+
 				return null;
 			}
 		}

ILSpy/TextView/DecompilerTextView.cs

@@ -170,7 +170,7 @@ namespace ICSharpCode.ILSpy.TextView
 
 		#region Line margin
 
-		void CurrentDisplaySettings_PropertyChanged(object sender, PropertyChangedEventArgs e)
+		void CurrentDisplaySettings_PropertyChanged(object? sender, PropertyChangedEventArgs e)
 		{
 			if (e.PropertyName == nameof(DisplaySettings.ShowLineNumbers))
 			{
@@ -216,7 +216,7 @@ namespace ICSharpCode.ILSpy.TextView
 			int offset = textEditor.Document.GetOffset(position.Value.Location);
 			if (referenceElementGenerator.References == null)
 				return;
-			ReferenceSegment seg = referenceElementGenerator.References.FindSegmentsContaining(offset).FirstOrDefault();
+			ReferenceSegment? seg = referenceElementGenerator.References.FindSegmentsContaining(offset).FirstOrDefault();
 			if (seg == null)
 				return;
 			object? content = GenerateTooltip(seg);
@@ -363,7 +363,7 @@ namespace ICSharpCode.ILSpy.TextView
 			TryCloseExistingPopup(true);
 		}
 
-		void ToolTipClosed(object sender, EventArgs e)
+		void ToolTipClosed(object? sender, EventArgs e)
 		{
 			if (toolTip == sender)
 			{
@@ -373,7 +373,10 @@ namespace ICSharpCode.ILSpy.TextView
 			{
 				// Because popupToolTip instances are created by the tooltip provider,
 				// they might be reused; so we should detach the event handler
-				popupToolTip.Closed -= ToolTipClosed;
+				if (popupToolTip != null)
+				{
+					popupToolTip.Closed -= ToolTipClosed;
+				}
 				popupToolTip = null;
 			}
 		}
@@ -515,7 +518,7 @@ namespace ICSharpCode.ILSpy.TextView
 		#endregion
 
 		#region Highlight brackets
-		void HighlightBrackets(object sender, EventArgs e)
+		void HighlightBrackets(object? sender, EventArgs e)
 		{
 			if (DisplaySettingsPanel.CurrentDisplaySettings.HighlightMatchingBraces)
 			{
@@ -569,7 +572,9 @@ namespace ICSharpCode.ILSpy.TextView
 			currentCancellationTokenSource = myCancellationTokenSource;
 			// cancel the previous only after current was set to the new one (avoid that the old one still finishes successfully)
 			if (previousCancellationTokenSource != null)
+			{
 				previousCancellationTokenSource.Cancel();
+			}
 
 			var tcs = new TaskCompletionSource<T>();
 			Task<T> task;
@@ -1248,29 +1253,52 @@ namespace ICSharpCode.ILSpy.TextView
 		{
 			return other != null
 				&& ViewedUri == other.ViewedUri
-				&& (DecompiledNodes == other.DecompiledNodes || DecompiledNodes?.SetEquals(other.DecompiledNodes) == true);
+				&& NullSafeSetEquals(DecompiledNodes, other.DecompiledNodes);
+
+			static bool NullSafeSetEquals(HashSet<ILSpyTreeNode>? a, HashSet<ILSpyTreeNode>? b)
+			{
+				if (a == b)
+					return true;
+				if (a == null || b == null)
+					return false;
+				return a.SetEquals(b);
+			}
 		}
 	}
 
 	public class DecompilerTextViewState : ViewState
 	{
-		private List<Tuple<int, int>>? ExpandedFoldings;
+		private List<(int StartOffset, int EndOffset)>? ExpandedFoldings;
 		private int FoldingsChecksum;
 		public double VerticalOffset;
 		public double HorizontalOffset;
 
 		public void SaveFoldingsState(IEnumerable<FoldingSection> foldings)
 		{
-			ExpandedFoldings = foldings.Where(f => !f.IsFolded).Select(f => Tuple.Create(f.StartOffset, f.EndOffset)).ToList();
-			FoldingsChecksum = unchecked(foldings.Select(f => f.StartOffset * 3 - f.EndOffset).DefaultIfEmpty().Aggregate((a, b) => a + b));
+			ExpandedFoldings = foldings.Where(f => !f.IsFolded)
+				.Select(f => (f.StartOffset, f.EndOffset)).ToList();
+			FoldingsChecksum = unchecked(foldings.Select(f => f.StartOffset * 3 - f.EndOffset)
+				.DefaultIfEmpty()
+				.Aggregate((a, b) => a + b));
 		}
 
 		internal void RestoreFoldings(List<NewFolding> list)
 		{
-			var checksum = unchecked(list.Select(f => f.StartOffset * 3 - f.EndOffset).DefaultIfEmpty().Aggregate((a, b) => a + b));
+			if (ExpandedFoldings == null)
+				return;
+			var checksum = unchecked(list.Select(f => f.StartOffset * 3 - f.EndOffset)
+				.DefaultIfEmpty()
+				.Aggregate((a, b) => a + b));
 			if (FoldingsChecksum == checksum)
+			{
 				foreach (var folding in list)
-					folding.DefaultClosed = !ExpandedFoldings.Any(f => f.Item1 == folding.StartOffset && f.Item2 == folding.EndOffset);
+				{
+					folding.DefaultClosed = !ExpandedFoldings.Any(
+						f => f.StartOffset == folding.StartOffset
+							&& f.EndOffset == folding.EndOffset
+					);
+				}
+			}
 		}
 
 		public override bool Equals(ViewState? other)
@@ -1301,17 +1329,21 @@ namespace ICSharpCode.ILSpy.TextView
 
 			resourceName += ".xshd";
 
-			manager.RegisterHighlighting(
-				name, extensions,
-				delegate {
-					using (Stream s = typeof(DecompilerTextView).Assembly.GetManifestResourceStream(typeof(DecompilerTextView), resourceName))
-					{
-						using (XmlTextReader reader = new XmlTextReader(s))
+			Stream? resourceStream = typeof(DecompilerTextView).Assembly
+				.GetManifestResourceStream(typeof(DecompilerTextView), resourceName);
+
+			if (resourceStream != null)
+			{
+				manager.RegisterHighlighting(
+					name, extensions,
+					delegate {
+						using (resourceStream)
+						using (XmlTextReader reader = new XmlTextReader(resourceStream))
 						{
 							return HighlightingLoader.Load(reader, manager);
 						}
-					}
-				});
+					});
+			}
 		}
 	}
 }