Fix #2534: Handle default implementations of properties and events in interfaces.

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

@@ -67,9 +67,35 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		public interface IA2 : IA
 		{
 #if CS80
+			int IA.Property3 {
+				get {
+					return 0;
+				}
+				set {
+				}
+			}
+
+			event EventHandler IA.MyEvent {
+				add {
+				}
+				remove {
+				}
+			}
+
+			new event EventHandler MyEvent {
+				add {
+				}
+				remove {
+				}
+			}
+
 			void IA.InternalMethod()
 			{
 			}
+
+			new void Method()
+			{
+			}
 #endif
 		}
 		public interface IB

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -1857,16 +1857,19 @@ namespace ICSharpCode.Decompiler.CSharp
 			var watch = System.Diagnostics.Stopwatch.StartNew();
 			try
 			{
+				bool adderHasBody = ev.CanAdd && ev.AddAccessor.HasBody;
+				bool removerHasBody = ev.CanRemove && ev.RemoveAccessor.HasBody;
 				var typeSystemAstBuilder = CreateAstBuilder(decompileRun.Settings);
-				typeSystemAstBuilder.UseCustomEvents = ev.DeclaringTypeDefinition.Kind != TypeKind.Interface;
+				typeSystemAstBuilder.UseCustomEvents = ev.DeclaringTypeDefinition.Kind != TypeKind.Interface
+					|| ev.IsExplicitInterfaceImplementation
+					|| adderHasBody
+					|| removerHasBody;
 				var eventDecl = typeSystemAstBuilder.ConvertEntity(ev);
 				int lastDot = ev.Name.LastIndexOf('.');
 				if (ev.IsExplicitInterfaceImplementation)
 				{
 					eventDecl.Name = ev.Name.Substring(lastDot + 1);
 				}
-				bool adderHasBody = ev.CanAdd && ev.AddAccessor.HasBody;
-				bool removerHasBody = ev.CanRemove && ev.RemoveAccessor.HasBody;
 				if (adderHasBody)
 				{
 					DecompileBody(ev.AddAccessor, ((CustomEventDeclaration)eventDecl).AddAccessor, decompileRun, decompilationContext);

ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs

@@ -992,7 +992,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			if (!ev.PrivateImplementationType.IsNull)
 				return null;
 			const Modifiers withoutBody = Modifiers.Abstract | Modifiers.Extern;
-			if ((ev.Modifiers & withoutBody) == 0 && ev.GetSymbol() is IEvent symbol && symbol.DeclaringType.Kind != TypeKind.Interface)
+			if ((ev.Modifiers & withoutBody) == 0 && ev.GetSymbol() is IEvent symbol)
 			{
 				if (!CheckAutomaticEventV4AggressivelyInlined(ev) && !CheckAutomaticEventV4(ev) && !CheckAutomaticEventV2(ev) && !CheckAutomaticEventV4MCS(ev))
 					return null;