Add MetadataTokenHelpers to avoid crashing when dealing with MetadataTokens

ICSharpCode.Decompiler/Disassembler/MethodBodyDisassembler.cs

@@ -310,7 +310,7 @@ namespace ICSharpCode.Decompiler.Disassembler
 					case OperandType.Type:
 						output.Write(' ');
 						int metadataToken = blob.ReadInt32();
-						EntityHandle? handle = TryAsEntityHandle(metadataToken);
+						EntityHandle? handle = MetadataTokenHelpers.TryAsEntityHandle(metadataToken);
 						try {
 							handle?.WriteTo(module, output, genericContext);
 						} catch (BadImageFormatException) {
@@ -321,7 +321,7 @@ namespace ICSharpCode.Decompiler.Disassembler
 					case OperandType.Tok:
 						output.Write(' ');
 						metadataToken = blob.ReadInt32();
-						handle = TryAsEntityHandle(metadataToken);
+						handle = MetadataTokenHelpers.TryAsEntityHandle(metadataToken);
 						switch (handle?.Kind) {
 							case HandleKind.MemberReference:
 								switch (metadata.GetMemberReference((MemberReferenceHandle)handle).GetKind()) {
@@ -426,19 +426,6 @@ namespace ICSharpCode.Decompiler.Disassembler
 			output.WriteLine();
 		}
 
-		private EntityHandle? TryAsEntityHandle(int metadataToken)
-		{
-			// SRM would interpret negative token values as virtual tokens,
-			// but that causes problems later on.
-			if (metadataToken < 0)
-				return null;
-			try {
-				return MetadataTokens.EntityHandle(metadataToken);
-			} catch (ArgumentException) {
-				return null;
-			}
-		}
-
 		private void WriteMetadataToken(EntityHandle handle, bool spaceBefore)
 		{
 			WriteMetadataToken(handle, MetadataTokens.GetToken(handle), spaceBefore);

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -269,6 +269,7 @@
     <Compile Include="CSharp\Transforms\AddXmlDocumentationTransform.cs" />
     <Compile Include="DecompileRun.cs" />
     <Compile Include="Disassembler\DomExtensions.cs" />
+    <Compile Include="Metadata\MetadataTokenHelpers.cs" />
     <Compile Include="Disassembler\OpCodeInfo.cs" />
     <Compile Include="Documentation\GetPotentiallyNestedClassTypeReference.cs" />
     <Compile Include="Documentation\IdStringMemberReference.cs" />

ICSharpCode.Decompiler/Metadata/MetadataTokenHelpers.cs

@@ -0,0 +1,55 @@
+// Copyright (c) 2018 Siegfried Pammer
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using System.Collections.Generic;
+using System.Reflection.Metadata;
+using System.Reflection.Metadata.Ecma335;
+using System.Text;
+
+namespace ICSharpCode.Decompiler.Metadata
+{
+	public static class MetadataTokenHelpers
+	{
+		public static EntityHandle? TryAsEntityHandle(int metadataToken)
+		{
+			// SRM would interpret negative token values as virtual tokens,
+			// but that causes problems later on.
+			if (metadataToken < 0)
+				return null;
+			try {
+				return MetadataTokens.EntityHandle(metadataToken);
+			} catch (ArgumentException) {
+				return null;
+			}
+		}
+
+		public static EntityHandle EntityHandleOrNil(int metadataToken)
+		{
+			// SRM would interpret negative token values as virtual tokens,
+			// but that causes problems later on.
+			if (metadataToken < 0)
+				return MetadataTokens.EntityHandle(0);
+			try {
+				return MetadataTokens.EntityHandle(metadataToken);
+			} catch (ArgumentException) {
+				return MetadataTokens.EntityHandle(0);
+			}
+		}
+	}
+}

ILSpy/Languages/CSharpLanguage.cs

@@ -339,7 +339,7 @@ namespace ICSharpCode.ILSpy
 					output.WriteLine();
 				}
 				var corHeader = module.Reader.PEHeaders.CorHeader;
-				var entrypointHandle = MetadataTokens.EntityHandle(corHeader.EntryPointTokenOrRelativeVirtualAddress);
+				var entrypointHandle = MetadataTokenHelpers.EntityHandleOrNil(corHeader.EntryPointTokenOrRelativeVirtualAddress);
 				if (!entrypointHandle.IsNil && entrypointHandle.Kind == HandleKind.MethodDefinition) {
 					var entrypoint = metadata.GetMethodDefinition((MethodDefinitionHandle)entrypointHandle);
 					output.Write("// Entry point: ");