From 6b075326f04b58d61096839a6e25b1148a157045 Mon Sep 17 00:00:00 2001
From: Siegfried Pammer <siegfriedpammer@gmail.com>
Date: Mon, 5 Aug 2019 23:09:02 +0200
Subject: [PATCH] Fix #1615: Handle nil tokens gracefully.

---
 ICSharpCode.Decompiler/IL/ILReader.cs                    | 3 ++-
 ICSharpCode.Decompiler/IL/InstructionOutputExtensions.cs | 6 ++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/ICSharpCode.Decompiler/IL/ILReader.cs b/ICSharpCode.Decompiler/IL/ILReader.cs
index 88b48da73..730198abf 100644
--- a/ICSharpCode.Decompiler/IL/ILReader.cs
+++ b/ICSharpCode.Decompiler/IL/ILReader.cs
@@ -124,9 +124,10 @@ namespace ICSharpCode.Decompiler.IL
 		EntityHandle ReadAndDecodeMetadataToken()
 		{
 			int token = reader.ReadInt32();
-			if (token < 0) {
+			if (token <= 0) {
 				// SRM uses negative tokens as "virtual tokens" and can get confused
 				// if we manually create them.
+				// Row-IDs < 1 are always invalid.
 				throw new BadImageFormatException("Invalid metadata token");
 			}
 			return MetadataTokens.EntityHandle(token);
diff --git a/ICSharpCode.Decompiler/IL/InstructionOutputExtensions.cs b/ICSharpCode.Decompiler/IL/InstructionOutputExtensions.cs
index d1aab3e59..b246ac5b9 100644
--- a/ICSharpCode.Decompiler/IL/InstructionOutputExtensions.cs
+++ b/ICSharpCode.Decompiler/IL/InstructionOutputExtensions.cs
@@ -69,8 +69,10 @@ namespace ICSharpCode.Decompiler.IL
 
 		public static void WriteTo(this EntityHandle entity, PEFile module, ITextOutput output, Metadata.GenericContext genericContext, ILNameSyntax syntax = ILNameSyntax.Signature)
 		{
-			if (entity.IsNil)
-				throw new ArgumentNullException(nameof(entity));
+			if (entity.IsNil) {
+				output.Write("<nil>");
+				return;
+			}
 			if (module == null)
 				throw new ArgumentNullException(nameof(module));
 			var metadata = module.Metadata;