Difficulties with std.variant.Algebraic

[bearophile]

Meta:

> I don't know whether to laugh or cry.

Algebraic has several problems, but your code has other problems.

I suggest to take a look at Nullable, especially the version that 
makes a constant value the "null".

Also try to almost never use cast() in your code, unless you 
_really_ know what you are doing.

Expecting a bit of magic from the D compiler is OK. But someone 
has to ask for it in a clean way, someone has to implement it, 
and someone else has to accept it.

Ask if you need more help.

Bye,
bearophile