convert default(T) to Nothing and typeof() to GetType()

ICSharpCode.NRefactory.VB/OutputVisitor/OutputVisitor.cs

@@ -419,7 +419,14 @@ namespace ICSharpCode.NRefactory.VB
 		
 		public object VisitGetTypeExpression(GetTypeExpression getTypeExpression, object data)
 		{
-			throw new NotImplementedException();
+			StartNode(getTypeExpression);
+			
+			WriteKeyword("GetType");
+			LPar();
+			getTypeExpression.Type.AcceptVisitor(this, data);
+			RPar();
+			
+			return EndNode(getTypeExpression);
 		}
 		
 		public object VisitTypeOfIsExpression(TypeOfIsExpression typeOfIsExpression, object data)

ICSharpCode.NRefactory.VB/Visitors/CSharpToVBConverterVisitor.cs

@@ -204,7 +204,8 @@ namespace ICSharpCode.NRefactory.VB.Visitors
 		
 		public AstNode VisitDefaultValueExpression(CSharp.DefaultValueExpression defaultValueExpression, object data)
 		{
-			throw new NotImplementedException();
+			// Nothing is equivalent to default(T) for reference and value types.
+			return EndNode(defaultValueExpression, new PrimitiveExpression(null));
 		}
 		
 		public AstNode VisitDirectionExpression(CSharp.DirectionExpression directionExpression, object data)
@@ -316,7 +317,9 @@ namespace ICSharpCode.NRefactory.VB.Visitors
 		
 		public AstNode VisitTypeOfExpression(CSharp.TypeOfExpression typeOfExpression, object data)
 		{
-			throw new NotImplementedException();
+			var expr = new GetTypeExpression();
+			expr.Type = (AstType)typeOfExpression.Type.AcceptVisitor(this, data);
+			return EndNode(typeOfExpression, expr);
 		}
 		
 		public AstNode VisitTypeReferenceExpression(CSharp.TypeReferenceExpression typeReferenceExpression, object data)