Fixed NotSupportedException when stepping into a decompiled generic method. (crash #3606)

src/AddIns/Debugger/Debugger.Core/IDStringProvider.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Reflection;
 using System.Text;
+using Debugger.MetaData;
 
 namespace Debugger
 {
@@ -42,7 +43,11 @@ namespace Debugger
 					MethodInfo mr = (MethodInfo)member;
 					if (mr.IsGenericMethod) {
 						b.Append("``");
-						b.Append(mr.GetGenericArguments().Length);
+						// DebugMethodInfo does not implement GetGenericArguments
+						if (mr is DebugMethodInfo)
+							b.Append(((DebugMethodInfo)mr).GenericParameterCount);
+						else
+							b.Append(mr.GetGenericArguments().Length);
 					}
 					parameters = mr.GetParameters();
 					if (mr.Name == "op_Implicit" || mr.Name == "op_Explicit") {

src/AddIns/Debugger/Debugger.Core/MetaData/DebugMethodInfo.cs

@@ -195,6 +195,13 @@ namespace Debugger.MetaData
 			get { return this.MethodDefSig.GenericParameterCount > 0; }
 		}
 		
+		/// <summary>
+		/// Gets the number of generic parameters on this method.
+		/// </summary>
+		public int GenericParameterCount {
+			get { return this.MethodDefSig.GenericParameterCount; }
+		}
+		
 		/// <inheritdoc/>
 		public override RuntimeMethodHandle MethodHandle {
 			get { throw new NotSupportedException(); }