using regex at compile time errors out! Error: static variable `thompsonFactory` cannot be read at compile time

[Brett via Digitalmars-d-learn]

                auto r = replaceAll!((C)
                                {
                                        return "X";
                                }
                                )(s, regex(`Y`));
Error: static variable `thompsonFactory` cannot be read at 
compile time

This is when the result is tried to be determined at compile 
time, e.g., assigning it to an enum even though s is known at 
compile time.