Support virtual modifier on static abstract interface members.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/StaticAbstractInterfaceMembers.cs

@@ -2,16 +2,54 @@
 
 namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty.StaticAbstractInterfaceMembers
 {
-	public interface I
+	internal interface I<T> where T : I<T>
+	{
+		static abstract T P { get; set; }
+		static abstract event Action E;
+		static abstract void M();
+		static abstract T operator +(T l, T r);
+		static abstract bool operator ==(T l, T r);
+		static abstract bool operator !=(T l, T r);
+		static abstract implicit operator T(string s);
+		static abstract explicit operator string(T t);
+	}
+
+	public interface IAmSimple
 	{
 		static abstract int Capacity { get; }
 		static abstract int Count { get; set; }
 		static abstract int SetterOnly { set; }
 		static abstract event EventHandler E;
-		static abstract I CreateI();
+		static abstract IAmSimple CreateI();
+	}
+
+	internal interface IAmStatic<T> where T : IAmStatic<T>
+	{
+		static T P { get; set; }
+		static event Action E;
+		static void M()
+		{
+		}
+		static T operator +(IAmStatic<T> l, T r)
+		{
+			throw new NotImplementedException();
+		}
+	}
+
+	internal interface IAmVirtual<T> where T : IAmVirtual<T>
+	{
+		static virtual T P { get; set; }
+		static virtual event Action E;
+		static virtual void M()
+		{
+		}
+		static virtual T operator +(T l, T r)
+		{
+			throw new NotImplementedException();
+		}
 	}
 
-	public class X : I
+	public class X : IAmSimple
 	{
 		public static int Capacity { get; }
 
@@ -24,13 +62,13 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty.StaticAbstractInterfaceM
 
 		public static event EventHandler E;
 
-		public static I CreateI()
+		public static IAmSimple CreateI()
 		{
 			return new X();
 		}
 	}
 
-	public class X2 : I
+	public class X2 : IAmSimple
 	{
 		public static int Capacity {
 			get {
@@ -61,7 +99,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty.StaticAbstractInterfaceM
 			}
 		}
 
-		public static I CreateI()
+		public static IAmSimple CreateI()
 		{
 			throw new NotImplementedException();
 		}

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -2373,8 +2373,14 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 						{
 							m |= Modifiers.Sealed;
 						}
-						if (member.IsAbstract && member.IsStatic)
-							m |= Modifiers.Abstract;
+						if (member.IsStatic)
+						{
+							// modifiers of static members in interfaces:
+							if (member.IsAbstract)
+								m |= Modifiers.Abstract;
+							else if (member.IsVirtual && !member.IsOverride)
+								m |= Modifiers.Virtual;
+						}
 					}
 					else
 					{

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataMethod.cs

@@ -576,8 +576,23 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		public bool IsStatic => (attributes & MethodAttributes.Static) != 0;
 		public bool IsAbstract => (attributes & MethodAttributes.Abstract) != 0;
 		public bool IsSealed => (attributes & (MethodAttributes.Abstract | MethodAttributes.Final | MethodAttributes.NewSlot | MethodAttributes.Static)) == MethodAttributes.Final;
-		public bool IsVirtual => (attributes & (MethodAttributes.Abstract | MethodAttributes.Virtual | MethodAttributes.NewSlot | MethodAttributes.Final)) == (MethodAttributes.Virtual | MethodAttributes.NewSlot);
-		public bool IsOverride => (attributes & (MethodAttributes.NewSlot | MethodAttributes.Virtual)) == MethodAttributes.Virtual;
+
+		public bool IsVirtual {
+			get {
+				if (IsStatic)
+				{
+					return (attributes & (MethodAttributes.Abstract | MethodAttributes.Virtual)) == MethodAttributes.Virtual;
+				}
+				else
+				{
+					const MethodAttributes mask = MethodAttributes.Abstract | MethodAttributes.Virtual
+						| MethodAttributes.NewSlot | MethodAttributes.Final;
+					return (attributes & mask) == (MethodAttributes.Virtual | MethodAttributes.NewSlot);
+				}
+			}
+		}
+
+		public bool IsOverride => (attributes & (MethodAttributes.NewSlot | MethodAttributes.Virtual | MethodAttributes.Static)) == MethodAttributes.Virtual;
 		public bool IsOverridable
 			=> (attributes & (MethodAttributes.Abstract | MethodAttributes.Virtual)) != 0
 			&& (attributes & MethodAttributes.Final) == 0;