Fix #1609: Decompilation of cached delegate-construction with unknown delegate type.

ICSharpCode.Decompiler/IL/Instructions.cs

@@ -786,7 +786,7 @@ namespace ICSharpCode.Decompiler.IL
 			clone.CloneVariables();
 			return clone;
 		}
-		public override StackType ResultType { get { return StackType.O; } }
+		public override StackType ResultType { get { return DelegateType?.GetStackType() ?? StackType.O; } }
 		public override void AcceptVisitor(ILVisitor visitor)
 		{
 			visitor.VisitILFunction(this);

ICSharpCode.Decompiler/IL/Instructions.tt

@@ -51,7 +51,7 @@
 			CustomChildren(new [] {
 				new ChildInfo("body"),
 				new ChildInfo("localFunctions") { IsCollection = true, Type = "ILFunction" }
-			}), CustomConstructor, CustomWriteTo, CustomComputeFlags, CustomVariableName("function"), ResultType("O")
+			}), CustomConstructor, CustomWriteTo, CustomComputeFlags, CustomVariableName("function"), ResultType("DelegateType?.GetStackType() ?? StackType.O")
 		),
 		new OpCode("BlockContainer", "A container of IL blocks.",
 			ResultType("this.ExpectedResultType"), CustomConstructor, CustomVariableName("container"),

ICSharpCode.Decompiler/IL/Transforms/CachedDelegateInitialization.cs

@@ -68,7 +68,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				return false;
 			if (!storeInst.MatchStsFld(out IField field2, out ILInstruction value) || !field.Equals(field2) || !field.IsCompilerGeneratedOrIsInCompilerGeneratedClass())
 				return false;
-			if (!DelegateConstruction.IsDelegateConstruction(value as NewObj, true))
+			if (!DelegateConstruction.IsDelegateConstruction(value.UnwrapConv(ConversionKind.Invalid) as NewObj, true))
 				return false;
 			var nextInstruction = inst.Parent.Children.ElementAtOrDefault(inst.ChildIndex + 1);
 			if (nextInstruction == null)

ICSharpCode.Decompiler/IL/Transforms/DelegateConstruction.cs

@@ -62,11 +62,13 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 
 		internal static bool IsDelegateConstruction(NewObj inst, bool allowTransformed = false)
 		{
-			if (inst == null || inst.Arguments.Count != 2 || inst.Method.DeclaringType.Kind != TypeKind.Delegate)
+			if (inst == null || inst.Arguments.Count != 2)
 				return false;
 			var opCode = inst.Arguments[1].OpCode;
-			
-			return opCode == OpCode.LdFtn || opCode == OpCode.LdVirtFtn || (allowTransformed && opCode == OpCode.ILFunction);
+			if (!(opCode == OpCode.LdFtn || opCode == OpCode.LdVirtFtn || (allowTransformed && opCode == OpCode.ILFunction)))
+				return false;
+			var typeKind = inst.Method.DeclaringType.Kind;
+			return typeKind == TypeKind.Delegate || typeKind == TypeKind.Unknown;
 		}
 		
 		static bool IsAnonymousMethod(ITypeDefinition decompiledTypeDefinition, IMethod method)