From fbe4a1b2dba68e5056671006db63a884c1b6fe8f Mon Sep 17 00:00:00 2001
From: Siegfried Pammer <siegfriedpammer@gmail.com>
Date: Wed, 1 Nov 2017 13:54:19 +0100
Subject: [PATCH] Fix #958: Invalid cast in generic class for abstract base
 call

---
 .../TestCases/Correctness/Generics.cs         | 26 ++++++++++++++++++-
 ICSharpCode.Decompiler/NRExtensions.cs        |  2 +-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/ICSharpCode.Decompiler.Tests/TestCases/Correctness/Generics.cs b/ICSharpCode.Decompiler.Tests/TestCases/Correctness/Generics.cs
index 0ff0b26a5..df65be4f2 100644
--- a/ICSharpCode.Decompiler.Tests/TestCases/Correctness/Generics.cs
+++ b/ICSharpCode.Decompiler.Tests/TestCases/Correctness/Generics.cs
@@ -57,11 +57,35 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 		}
 	}
 
-	public class BaseClass
+	public abstract class BaseClass
 	{
+		protected abstract void Method1<T>(T test);
 	}
 
 	public class DerivedClass : BaseClass
 	{
+		protected override void Method1<T>(T test) { }
+
+		private void Method2()
+		{
+			this.Method1(0);
+		}
+	}
+
+	#region Issue 958 - Invalid cast in generic class for abstract base call
+	internal abstract class BaseClass<T>
+	{
+		protected abstract void Method1();
+	}
+
+	internal class DerivedClass<T> : BaseClass<T>
+	{
+		protected override void Method1() { }
+
+		private void Method2()
+		{
+			this.Method1();
+		}
 	}
+	#endregion
 }
diff --git a/ICSharpCode.Decompiler/NRExtensions.cs b/ICSharpCode.Decompiler/NRExtensions.cs
index 4e72c08ab..3f0a5c38a 100644
--- a/ICSharpCode.Decompiler/NRExtensions.cs
+++ b/ICSharpCode.Decompiler/NRExtensions.cs
@@ -31,7 +31,7 @@ namespace ICSharpCode.Decompiler
 			if (decompilationContext.CurrentTypeDefinition != null)
 				classTypeParameters = decompilationContext.CurrentTypeDefinition.TypeArguments;
 			IMethod method = decompilationContext.CurrentMember as IMethod;
-			if (method != null)
+			if (method != null && method.TypeParameters.Count > 0)
 				methodTypeParameters = method.TypeArguments;
 			if (typeSystem is SpecializingDecompilerTypeSystem)
 				typeSystem = ((SpecializingDecompilerTypeSystem)typeSystem).Context;