Fixed NullReferenceException errors caused by unresolved references.

ICSharpCode.Decompiler/Ast/AstBuilder.cs

@@ -624,10 +624,14 @@ namespace ICSharpCode.Decompiler.Ast
 			if (!methodDef.DeclaringType.IsInterface) {
 				if (!methodDef.HasOverrides) {
 					astMethod.Modifiers = ConvertModifiers(methodDef);
-					if (methodDef.IsVirtual ^ !methodDef.IsNewSlot) {
-						if (TypesHierarchyHelpers.FindBaseMethods(methodDef).Any())
-							astMethod.Modifiers |= Modifiers.New;
-					}
+					if (methodDef.IsVirtual ^ !methodDef.IsNewSlot)
+						try {
+							if (TypesHierarchyHelpers.FindBaseMethods(methodDef).Any())
+								astMethod.Modifiers |= Modifiers.New;
+						}
+						catch (ReferenceResolvingException) {
+							// TODO: add some kind of notification (a comment?) about possible problems with decompiled code due to unresolved references.
+						}
 				} else
 					astMethod.PrivateImplementationType = ConvertType(methodDef.Overrides.First().DeclaringType);
 				astMethod.Body = CreateMethodBody(methodDef, astMethod.Parameters);
@@ -739,17 +743,23 @@ namespace ICSharpCode.Decompiler.Ast
 				getterModifiers = ConvertModifiers(propDef.GetMethod);
 				setterModifiers = ConvertModifiers(propDef.SetMethod);
 				astProp.Modifiers = FixUpVisibility(getterModifiers | setterModifiers);
-				if (accessor.IsVirtual && !accessor.IsNewSlot && (propDef.GetMethod == null || propDef.SetMethod == null))
-					foreach (var basePropDef in TypesHierarchyHelpers.FindBaseProperties(propDef))
-						if (basePropDef.GetMethod != null && basePropDef.SetMethod != null) {
-					var propVisibilityModifiers = ConvertModifiers(basePropDef.GetMethod) | ConvertModifiers(basePropDef.SetMethod);
-					astProp.Modifiers = FixUpVisibility((astProp.Modifiers & ~Modifiers.VisibilityMask) | (propVisibilityModifiers & Modifiers.VisibilityMask));
-					break;
-				} else if ((basePropDef.GetMethod ?? basePropDef.SetMethod).IsNewSlot)
-					break;
-				if (accessor.IsVirtual ^ !accessor.IsNewSlot) {
-					if (TypesHierarchyHelpers.FindBaseProperties(propDef).Any())
-						astProp.Modifiers |= Modifiers.New;
+				try {
+					if (accessor.IsVirtual && !accessor.IsNewSlot && (propDef.GetMethod == null || propDef.SetMethod == null))
+						foreach (var basePropDef in TypesHierarchyHelpers.FindBaseProperties(propDef))
+							if (basePropDef.GetMethod != null && basePropDef.SetMethod != null) {
+								var propVisibilityModifiers = ConvertModifiers(basePropDef.GetMethod) | ConvertModifiers(basePropDef.SetMethod);
+								astProp.Modifiers = FixUpVisibility((astProp.Modifiers & ~Modifiers.VisibilityMask) | (propVisibilityModifiers & Modifiers.VisibilityMask));
+								break;
+							} else if ((basePropDef.GetMethod ?? basePropDef.SetMethod).IsNewSlot)
+								break;
+
+					if (accessor.IsVirtual ^ !accessor.IsNewSlot) {
+						if (TypesHierarchyHelpers.FindBaseProperties(propDef).Any())
+							astProp.Modifiers |= Modifiers.New;
+					}
+				}
+				catch (ReferenceResolvingException) {
+					// TODO: add some kind of notification (a comment?) about possible problems with decompiled code due to unresolved references.
 				}
 			}
 			astProp.Name = CleanName(propDef.Name);

ICSharpCode.Decompiler/Ast/TypesHierarchyHelpers.cs

@@ -14,9 +14,9 @@ namespace ICSharpCode.Decompiler.Ast
 			if (resolveTypeArguments)
 				return BaseTypes(derivedType).Any(t => t.Item == baseType);
 			else {
-				var comparableBaseType = baseType.Resolve();
+				var comparableBaseType = baseType.ResolveOrThrow();
 				while (derivedType.BaseType != null) {
-					var resolvedBaseType = derivedType.BaseType.Resolve();
+					var resolvedBaseType = derivedType.BaseType.ResolveOrThrow();
 					if (resolvedBaseType == null)
 						return false;
 					if (comparableBaseType == resolvedBaseType)
@@ -29,11 +29,16 @@ namespace ICSharpCode.Decompiler.Ast
 
 		public static bool IsBaseMethod(MethodDefinition parentMethod, MethodDefinition childMethod)
 		{
+			if (parentMethod == null)
+				throw new ArgumentNullException("parentMethod");
+			if (childMethod == null)
+				throw new ArgumentNullException("childMethod");
+
 			if (parentMethod.Name != childMethod.Name)
 				return false;
 
 			if (parentMethod.HasParameters || childMethod.HasParameters)
-				if(!parentMethod.HasParameters || ! childMethod.HasParameters || parentMethod.Parameters.Count != childMethod.Parameters.Count)
+				if (!parentMethod.HasParameters || !childMethod.HasParameters || parentMethod.Parameters.Count != childMethod.Parameters.Count)
 					return false;
 
 			return FindBaseMethods(childMethod).Any(m => m == parentMethod);// || (parentMethod.HasGenericParameters && m.);
@@ -41,6 +46,11 @@ namespace ICSharpCode.Decompiler.Ast
 
 		public static bool IsBaseProperty(PropertyDefinition parentProperty, PropertyDefinition childProperty)
 		{
+			if (parentProperty == null)
+				throw new ArgumentNullException("parentProperty");
+			if (childProperty == null)
+				throw new ArgumentNullException("childProperty");
+
 			if (parentProperty.Name != childProperty.Name)
 				return false;
 
@@ -53,6 +63,9 @@ namespace ICSharpCode.Decompiler.Ast
 
 		public static IEnumerable<MethodDefinition> FindBaseMethods(MethodDefinition method)
 		{
+			if (method == null)
+				throw new ArgumentNullException("method");
+
 			var typeContext = CreateGenericContext(method.DeclaringType);
 			var gMethod = typeContext.ApplyTo(method);
 
@@ -65,8 +78,11 @@ namespace ICSharpCode.Decompiler.Ast
 					}
 		}
 
-		public static IEnumerable<PropertyDefinition> FindBaseProperties(PropertyDefinition property)
+		public static IEnumerable<PropertyDefinition> FindBaseProperties(PropertyDefinition property, bool ignoreResolveExceptions = false)
 		{
+			if (property == null)
+				throw new ArgumentNullException("property");
+
 			var typeContext = CreateGenericContext(property.DeclaringType);
 			var gProperty = typeContext.ApplyTo(property);
 
@@ -109,7 +125,7 @@ namespace ICSharpCode.Decompiler.Ast
 			if (mCandidate.HasOverrides)
 				return false;
 
-			if (!IsSameType(candidate.Resolve(mCandidate.ReturnType), method.Resolve(mMethod.ReturnType)))
+			if (!IsSameType(candidate.ResolveWithContext(mCandidate.ReturnType), method.ResolveWithContext(mMethod.ReturnType)))
 				return false;
 
 			if (mCandidate.HasGenericParameters || mMethod.HasGenericParameters) {
@@ -140,7 +156,7 @@ namespace ICSharpCode.Decompiler.Ast
 			if ((mCandidate.GetMethod ?? mCandidate.SetMethod).HasOverrides)
 				return false;
 
-			if (!IsSameType(candidate.Resolve(mCandidate.PropertyType), property.Resolve(mProperty.PropertyType)))
+			if (!IsSameType(candidate.ResolveWithContext(mCandidate.PropertyType), property.ResolveWithContext(mProperty.PropertyType)))
 				return false;
 
 			if (mCandidate.HasParameters || mProperty.HasParameters) {
@@ -158,8 +174,8 @@ namespace ICSharpCode.Decompiler.Ast
 
 		private static bool MatchParameters(GenericContext<ParameterDefinition> baseParameterType, GenericContext<ParameterDefinition> parameterType)
 		{
-			var baseParam = baseParameterType.Resolve(baseParameterType.Item.ParameterType);
-			var param = parameterType.Resolve(parameterType.Item.ParameterType);
+			var baseParam = baseParameterType.ResolveWithContext(baseParameterType.Item.ParameterType);
+			var param = parameterType.ResolveWithContext(parameterType.Item.ParameterType);
 			return IsSameType(baseParam, param);
 		}
 
@@ -186,10 +202,10 @@ namespace ICSharpCode.Decompiler.Ast
 				var baseType = type.Item.BaseType;
 				var genericBaseType = baseType as GenericInstanceType;
 				if (genericBaseType != null) {
-					type = new GenericContext<TypeDefinition>(genericBaseType.Resolve(),
-						genericBaseType.GenericArguments.Select(t => type.Resolve(t)));
+					type = new GenericContext<TypeDefinition>(genericBaseType.ResolveOrThrow(),
+						genericBaseType.GenericArguments.Select(t => type.ResolveWithContext(t)));
 				} else
-					type = new GenericContext<TypeDefinition>(baseType.Resolve());
+					type = new GenericContext<TypeDefinition>(baseType.ResolveOrThrow());
 				yield return type;
 			}
 		}
@@ -201,7 +217,7 @@ namespace ICSharpCode.Decompiler.Ast
 				: new GenericContext<TypeDefinition>(type);
 		}
 
-		struct GenericContext<T>
+		struct GenericContext<T> where T : class
 		{
 			private static readonly ReadOnlyCollection<TypeReference> Empty = new ReadOnlyCollection<TypeReference>(new List<TypeReference>());
 
@@ -210,12 +226,18 @@ namespace ICSharpCode.Decompiler.Ast
 
 			public GenericContext(T item)
 			{
+				if (item == null)
+					throw new ArgumentNullException("item");
+
 				Item = item;
 				TypeArguments = Empty;
 			}
 
 			public GenericContext(T item, IEnumerable<TypeReference> typeArguments)
 			{
+				if (item == null)
+					throw new ArgumentNullException("item");
+
 				Item = item;
 				var list = new List<TypeReference>();
 				foreach (var arg in typeArguments) {
@@ -231,7 +253,7 @@ namespace ICSharpCode.Decompiler.Ast
 				TypeArguments = typeArguments;
 			}
 
-			public TypeReference Resolve(TypeReference type)
+			public TypeReference ResolveWithContext(TypeReference type)
 			{
 				var genericParameter = type as GenericParameter;
 				if (genericParameter != null && genericParameter.Owner.GenericParameterType == GenericParameterType.Type) {
@@ -239,7 +261,7 @@ namespace ICSharpCode.Decompiler.Ast
 				}
 				var arrayType = type as ArrayType;
 				if (arrayType != null) {
-					var resolvedElementType = Resolve(arrayType.ElementType);
+					var resolvedElementType = ResolveWithContext(arrayType.ElementType);
 					if (resolvedElementType == null)
 						return null;
 					if (resolvedElementType == arrayType.ElementType)
@@ -249,10 +271,10 @@ namespace ICSharpCode.Decompiler.Ast
 						newArrayType.Dimensions[dimension] = arrayType.Dimensions[dimension];
 					return newArrayType;
 				}
-				return type.Resolve();
+				return type.ResolveOrThrow();
 			}
 
-			public GenericContext<T2> ApplyTo<T2>(T2 item)
+			public GenericContext<T2> ApplyTo<T2>(T2 item) where T2 : class
 			{
 				return new GenericContext<T2>(item, this.TypeArguments);
 			}

ICSharpCode.Decompiler/CecilExtensions.cs

@@ -185,7 +185,15 @@ namespace ICSharpCode.Decompiler
 			else
 				return null;
 		}
-		
+
+		public static TypeDefinition ResolveOrThrow(this TypeReference typeReference)
+		{
+			var resolved = typeReference.Resolve();
+			if (resolved == null)
+				throw new ReferenceResolvingException();
+			return resolved;
+		}
+
 		public static bool IsCompilerGenerated(this ICustomAttributeProvider provider)
 		{
 			if (provider != null && provider.HasCustomAttributes) {

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -110,6 +110,7 @@
     <Compile Include="ITextOutput.cs" />
     <Compile Include="PlainTextOutput.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="ReferenceResolvingException.cs" />
     <Compile Include="TextOutputWriter.cs" />
     <None Include="Properties\AssemblyInfo.template.cs" />
   </ItemGroup>

ICSharpCode.Decompiler/ReferenceResolvingException.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace ICSharpCode.Decompiler
+{
+	/// <summary>
+	/// Represents an error while resolving a reference to a type or a member.
+	/// </summary>
+	[Serializable]
+	public class ReferenceResolvingException : Exception
+	{
+		/// <summary>
+		/// Initializes a new instance of the <see cref="T:ResolveException"/> class
+		/// </summary>
+		public ReferenceResolvingException()
+		{
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="T:ResolveException"/> class
+		/// </summary>
+		/// <param name="message">A <see cref="T:System.String"/> that describes the error. The content of message is intended to be understood by humans. The caller of this constructor is required to ensure that this string has been localized for the current system culture.</param>
+		public ReferenceResolvingException(string message)
+			: base(message)
+		{
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="T:ResolveException"/> class
+		/// </summary>
+		/// <param name="message">A <see cref="T:System.String"/> that describes the error. The content of message is intended to be understood by humans. The caller of this constructor is required to ensure that this string has been localized for the current system culture.</param>
+		/// <param name="inner">The exception that is the cause of the current exception. If the innerException parameter is not a null reference, the current exception is raised in a catch block that handles the inner exception.</param>
+		public ReferenceResolvingException(string message, Exception inner)
+			: base(message, inner)
+		{
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="T:ResolveException"/> class
+		/// </summary>
+		/// <param name="info">The object that holds the serialized object data.</param>
+		/// <param name="context">The contextual information about the source or destination.</param>
+		protected ReferenceResolvingException(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context)
+			: base(info, context)
+		{
+		}
+	}
+}

ILSpy/TreeNodes/Analyzer/AnalyzedPropertyOverridesTreeNode.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading;
+using ICSharpCode.Decompiler;
 using ICSharpCode.Decompiler.Ast;
 using ICSharpCode.NRefactory.Utils;
 using ICSharpCode.TreeView;
@@ -69,18 +70,26 @@ namespace ICSharpCode.ILSpy.TreeNodes.Analyzer
 			foreach (TypeDefinition type in TreeTraversal.PreOrder(asm.AssemblyDefinition.MainModule.Types, t => t.NestedTypes)) {
 				ct.ThrowIfCancellationRequested();
 
-				if (!TypesHierarchyHelpers.IsBaseType(analyzedProperty.DeclaringType, type, resolveTypeArguments: false))
-					continue;
+				SharpTreeNode newNode = null;
+				try {
+					if (!TypesHierarchyHelpers.IsBaseType(analyzedProperty.DeclaringType, type, resolveTypeArguments: false))
+						continue;
 
-				foreach (PropertyDefinition property in type.Properties) {
-					ct.ThrowIfCancellationRequested();
+					foreach (PropertyDefinition property in type.Properties) {
+						ct.ThrowIfCancellationRequested();
 
-					if (TypesHierarchyHelpers.IsBaseProperty(analyzedProperty, property)) {
-						MethodDefinition anyAccessor = property.GetMethod ?? property.SetMethod;
-						bool hidesParent = !anyAccessor.IsVirtual ^ anyAccessor.IsNewSlot;
-						yield return new AnalyzedPropertyTreeNode(property, hidesParent ? "(hides) " : "");
+						if (TypesHierarchyHelpers.IsBaseProperty(analyzedProperty, property)) {
+							MethodDefinition anyAccessor = property.GetMethod ?? property.SetMethod;
+							bool hidesParent = !anyAccessor.IsVirtual ^ anyAccessor.IsNewSlot;
+							newNode = new AnalyzedPropertyTreeNode(property, hidesParent ? "(hides) " : "");
+						}
 					}
 				}
+				catch (ReferenceResolvingException) {
+					// ignore this type definition.
+				}
+				if (newNode != null)
+					yield return newNode;
 			}
 		}
 

ILSpy/TreeNodes/Analyzer/AnalyzerMethodOverridesTreeNode.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading;
+using ICSharpCode.Decompiler;
 using ICSharpCode.Decompiler.Ast;
 using ICSharpCode.NRefactory.Utils;
 using ICSharpCode.TreeView;
@@ -73,20 +74,25 @@ namespace ICSharpCode.ILSpy.TreeNodes.Analyzer
 			foreach (TypeDefinition type in TreeTraversal.PreOrder(asm.AssemblyDefinition.MainModule.Types, t => t.NestedTypes))
 			{
 				ct.ThrowIfCancellationRequested();
+				SharpTreeNode newNode = null;
+				try {
+					if (!TypesHierarchyHelpers.IsBaseType(analyzedMethod.DeclaringType, type, resolveTypeArguments: false))
+						continue;
 
-				if (!TypesHierarchyHelpers.IsBaseType(analyzedMethod.DeclaringType, type, resolveTypeArguments: false))
-					continue;
+					foreach (MethodDefinition method in type.Methods) {
+						ct.ThrowIfCancellationRequested();
 
-				foreach (MethodDefinition method in type.Methods)
-				{
-					ct.ThrowIfCancellationRequested();
-
-					if (TypesHierarchyHelpers.IsBaseMethod(analyzedMethod, method))
-					{
-						bool hidesParent = !method.IsVirtual ^ method.IsNewSlot;
-						yield return new AnalyzedMethodTreeNode(method, hidesParent ? "(hides) " : "");
+						if (TypesHierarchyHelpers.IsBaseMethod(analyzedMethod, method)) {
+							bool hidesParent = !method.IsVirtual ^ method.IsNewSlot;
+							newNode = new AnalyzedMethodTreeNode(method, hidesParent ? "(hides) " : "");
+						}
 					}
 				}
+				catch (ReferenceResolvingException) {
+					// ignore this type definition. maybe add a notification about such cases.
+				}
+				if (newNode != null)
+					yield return newNode;
 			}
 		}