From fdc109eebd9b05002c921e689b908de7dcb82f65 Mon Sep 17 00:00:00 2001
From: Daniel Grunwald <daniel@danielgrunwald.de>
Date: Sat, 14 Jul 2018 11:30:59 +0200
Subject: [PATCH] Fix NullReferenceException in TypeSystemAstBuilder when
 attribute argument decoding fails.

---
 .../CSharp/OutputVisitor/CSharpOutputVisitor.cs          | 2 +-
 .../CSharp/Syntax/TypeSystemAstBuilder.cs                | 9 ++++++++-
 ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj     | 1 -
 ICSharpCode.Decompiler/TypeSystem/IAttribute.cs          | 5 +++++
 .../TypeSystem/Implementation/CustomAttribute.cs         | 9 +++++++++
 .../TypeSystem/Implementation/DefaultAttribute.cs        | 4 +++-
 6 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs b/ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs
index 6ee369c5d..52445918c 100644
--- a/ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs
+++ b/ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs
@@ -1288,7 +1288,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 		{
 			StartNode(attribute);
 			attribute.Type.AcceptVisitor(this);
-			if (attribute.Arguments.Count != 0 || !attribute.GetChildByRole(Roles.LPar).IsNull) {
+			if (attribute.Arguments.Count != 0 || attribute.HasArgumentList) {
 				Space(policy.SpaceBeforeMethodCallParentheses);
 				WriteCommaSeparatedListInParenthesis(attribute.Arguments, policy.SpaceWithinMethodCallParentheses);
 			}
diff --git a/ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs b/ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs
index ee6dbe737..51964a4cf 100644
--- a/ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs
+++ b/ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs
@@ -471,9 +471,16 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				mt.MemberName = mt.MemberName.Substring(0, mt.MemberName.Length - 9);
 			}
 			var parameters = attribute.Constructor?.Parameters ?? EmptyList<IParameter>.Instance;
-			foreach (var (arg, p) in attribute.FixedArguments.ZipLongest(parameters)) {
+			for (int i = 0; i < attribute.FixedArguments.Length; i++) {
+				var arg = attribute.FixedArguments[i];
+				var p = (i < parameters.Count) ? parameters[i] : null;
 				attr.Arguments.Add(ConvertConstantValue(p?.Type ?? arg.Type, arg.Type, arg.Value));
 			}
+			if (attribute.HasDecodeErrors) {
+				attr.HasArgumentList = true;
+				attr.AddChild(new Comment("Could not decode attribute arguments.", CommentType.MultiLine), Roles.Comment);
+				attr.AddChild(new CSharpTokenNode(TextLocation.Empty, Roles.RPar), Roles.RPar);
+			}
 			if (attribute.NamedArguments.Length > 0) {
 				InitializedObjectResolveResult targetResult = new InitializedObjectResolveResult(attribute.AttributeType);
 				foreach (var namedArg in attribute.NamedArguments) {
diff --git a/ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj b/ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj
index 20331d7df..4826a9bab 100644
--- a/ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj
+++ b/ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj
@@ -274,7 +274,6 @@
     <Compile Include="Documentation\GetPotentiallyNestedClassTypeReference.cs" />
     <Compile Include="Documentation\IdStringMemberReference.cs" />
     <Compile Include="Documentation\IdStringProvider.cs" />
-    <Compile Include="Documentation\XmlDocKeyProvider.cs" />
     <Compile Include="Documentation\XmlDocLoader.cs" />
     <Compile Include="Documentation\XmlDocumentationProvider.cs" />
     <Compile Include="IL\ControlFlow\AsyncAwaitDecompiler.cs" />
diff --git a/ICSharpCode.Decompiler/TypeSystem/IAttribute.cs b/ICSharpCode.Decompiler/TypeSystem/IAttribute.cs
index 62b4f067b..e05f97769 100644
--- a/ICSharpCode.Decompiler/TypeSystem/IAttribute.cs
+++ b/ICSharpCode.Decompiler/TypeSystem/IAttribute.cs
@@ -40,6 +40,11 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		/// </summary>
 		IMethod Constructor { get; }
 
+		/// <summary>
+		/// Gets whether there were errors decoding the attribute.
+		/// </summary>
+		bool HasDecodeErrors { get; }
+
 		/// <summary>
 		/// Gets the positional arguments.
 		/// </summary>
diff --git a/ICSharpCode.Decompiler/TypeSystem/Implementation/CustomAttribute.cs b/ICSharpCode.Decompiler/TypeSystem/Implementation/CustomAttribute.cs
index 3a5616af7..3d58038b5 100644
--- a/ICSharpCode.Decompiler/TypeSystem/Implementation/CustomAttribute.cs
+++ b/ICSharpCode.Decompiler/TypeSystem/Implementation/CustomAttribute.cs
@@ -38,6 +38,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		// lazy-loaded:
 		CustomAttributeValue<IType> value;
 		bool valueDecoded;
+		bool hasDecodeErrors;
 
 		internal CustomAttribute(MetadataModule module, IMethod attrCtor, CustomAttributeHandle handle)
 		{
@@ -65,6 +66,13 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			}
 		}
 
+		public bool HasDecodeErrors {
+			get {
+				DecodeValue();
+				return hasDecodeErrors;
+			}
+		}
+
 		void DecodeValue()
 		{
 			lock (this) {
@@ -80,6 +88,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 						ImmutableArray<CustomAttributeTypedArgument<IType>>.Empty,
 						ImmutableArray<CustomAttributeNamedArgument<IType>>.Empty
 					);
+					hasDecodeErrors = true;
 					valueDecoded = true; // in case of errors, never try again.
 				}
 			}
diff --git a/ICSharpCode.Decompiler/TypeSystem/Implementation/DefaultAttribute.cs b/ICSharpCode.Decompiler/TypeSystem/Implementation/DefaultAttribute.cs
index e5bef0a92..ca3d4935b 100644
--- a/ICSharpCode.Decompiler/TypeSystem/Implementation/DefaultAttribute.cs
+++ b/ICSharpCode.Decompiler/TypeSystem/Implementation/DefaultAttribute.cs
@@ -66,7 +66,9 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		public IType AttributeType {
 			get { return attributeType; }
 		}
-		
+
+		bool IAttribute.HasDecodeErrors => false;
+
 		public IMethod Constructor {
 			get {
 				IMethod ctor = this.constructor;