Moved SpecializedMember property 'Substitution' to IMember and

SpecializedMethod property 'TypeArguments' to IMethod.
That should eliminate the need to upcast these objects & makes the
type system more flexible - that's needed for the
ReducedExtensionMethod model.

ICSharpCode.NRefactory.CSharp/Resolver/CSharpOperators.cs

@@ -227,7 +227,13 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			{
 				throw new NotSupportedException();
 			}
-			
+
+			TypeParameterSubstitution IMember.Substitution {
+				get {
+					return TypeParameterSubstitution.Identity;
+				}
+			}
+
 			string INamedElement.FullName {
 				get { return "operator"; }
 			}

ICSharpCode.NRefactory.CSharp/Resolver/ReducedExtensionMethod.cs

@@ -27,6 +27,7 @@ using System;
 using ICSharpCode.NRefactory.TypeSystem;
 using System.Collections.Generic;
 using System.Linq;
+using ICSharpCode.NRefactory.TypeSystem.Implementation;
 
 namespace ICSharpCode.NRefactory.CSharp
 {
@@ -143,6 +144,13 @@ namespace ICSharpCode.NRefactory.CSharp
 			}
 		}
 
+		public TypeParameterSubstitution Substitution {
+			get {
+				return baseMethod.Substitution;
+			}
+		}
+
+
 		#endregion
 
 		#region IMethod implementation
@@ -220,9 +228,16 @@ namespace ICSharpCode.NRefactory.CSharp
 		}
 
 		public IMethod ReducedFrom { 
-			get { return baseMethod; } 
+			get {
+				return baseMethod;
+			} 
 		}
 
+		public IList<IType> TypeArguments {
+			get {
+				return baseMethod.TypeArguments;
+			}
+		}
 		#endregion
 
 		#region IParameterizedMember implementation

ICSharpCode.NRefactory/TypeSystem/IMember.cs

@@ -170,5 +170,14 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// Otherwise, the main resolve context of a compilation is sufficient.
 		/// </remarks>
 		IMemberReference ToMemberReference();
+
+		/// <summary>
+		/// Gets the substitution belonging to this specialized member.
+		/// Returns TypeParameterSubstitution.Identity for not specialized members.
+		/// </summary>
+		TypeParameterSubstitution Substitution {
+			get;
+		}
+
 	}
 }

ICSharpCode.NRefactory/TypeSystem/IMethod.cs

@@ -97,7 +97,16 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		IList<IAttribute> ReturnTypeAttributes { get; }
 		
 		IList<ITypeParameter> TypeParameters { get; }
-		
+
+		/// <summary>
+		/// Gets the type arguments passed to this method.
+		/// If only the type parameters for the class were specified and the generic method
+		/// itself is not specialized yet, this property will return an empty list.
+		/// </summary>
+		IList<IType> TypeArguments {
+			get;
+		}
+
 		bool IsExtensionMethod { get; }
 		bool IsConstructor { get; }
 		bool IsDestructor { get; }

ICSharpCode.NRefactory/TypeSystem/Implementation/AbstractResolvedMember.cs

@@ -117,7 +117,11 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 		public bool IsOverridable {
 			get { return unresolved.IsOverridable; }
 		}
-		
+
+		public TypeParameterSubstitution Substitution {
+			get { return TypeParameterSubstitution.Identity; }
+		}
+
 		public virtual IMemberReference ToMemberReference()
 		{
 			var declTypeRef = this.DeclaringType.ToTypeReference();

ICSharpCode.NRefactory/TypeSystem/Implementation/DefaultResolvedMethod.cs

@@ -172,7 +172,10 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 		public IList<IParameter> Parameters { get; private set; }
 		public IList<IAttribute> ReturnTypeAttributes { get; private set; }
 		public IList<ITypeParameter> TypeParameters { get; private set; }
-		
+
+		static readonly IList<IType> emptyArguments = new IType[0];
+		public IList<IType> TypeArguments { get { return emptyArguments; } }
+
 		public bool IsExtensionMethod { get; private set; }
 		
 		public IList<IUnresolvedMethod> Parts {