JMD is right. Using inheritance for value types is a bad idea,
and it shouldn't be done.
The problem is that when you assign a derived value type to a
base value type, the members in the derived type are removed, and
this can lead to very weird behaviour. You could enforce that
derived value types can never add any members, but then what
would be the point? For adding virtual method calls for changing
behaviour?
Using inheritance for reference types only was one of the better
design decisions for D. If you want to treat a set of structs in
a similar way, you can do it better with parametric polymorphism
than with classes and virtual method calls.
