fix #531 - ICSharpCode.Decompiler.ReferenceResolvingException when Searching for Instantiations

ICSharpCode.Decompiler/Ast/TypesHierarchyHelpers.cs

@@ -32,9 +32,11 @@ namespace ICSharpCode.Decompiler.Ast
 			if (resolveTypeArguments)
 				return BaseTypes(derivedType).Any(t => t.Item == baseType);
 			else {
-				var comparableBaseType = baseType.ResolveOrThrow();
+				var comparableBaseType = baseType.Resolve();
+				if (comparableBaseType == null)
+					return false;
 				while (derivedType.BaseType != null) {
-					var resolvedBaseType = derivedType.BaseType.ResolveOrThrow();
+					var resolvedBaseType = derivedType.BaseType.Resolve();
 					if (resolvedBaseType == null)
 						return false;
 					if (comparableBaseType == resolvedBaseType)

ICSharpCode.Decompiler/CecilExtensions.cs

@@ -190,6 +190,7 @@ namespace ICSharpCode.Decompiler
 				return null;
 		}
 
+		[Obsolete("throwing exceptions is considered a bug")]
 		public static TypeDefinition ResolveOrThrow(this TypeReference typeReference)
 		{
 			var resolved = typeReference.Resolve();