public CSharpSyntaxNode Invoke(ParseExpressionVisitor visitor, IList <IParseTree> children)
{
var result = Defn.Invoke(visitor, children) as MethodDeclarationSyntax;
Macros.AddMacro(result, visitor.NamespaceName, visitor.ClassName);
return(result); // return the macro as a function so other programs can reference it.
}