Same situation happens when I assign reference data to
properties. I can check or do something with data at the moment
of assignment, but I can't control that someone will modify
using initial reference from outside. So do you copy reference
data in constructors or properties? Should it be? Or call site
should be responsible for not escaping reference somewhere
outside and not modifying these data badly?
I'd probably do one of three things:
* Clone a private copy;
* Pass the parameter as an immutable ref;
* Change the method signature to take a std.typecons.Unique!T
to express the fact that I want transfer of ownership.
Try to encode as much information as you can into the method
signature to describe your intentions.
