Dlang Polymorphism doesn't work as expected.

[Enjoys Math]

On Sunday, 4 September 2022 at 17:43:33 UTC, Enjoys Math wrote:
> On Sunday, 4 September 2022 at 17:38:54 UTC, Enjoys Math wrote:
>> On Sunday, 4 September 2022 at 17:36:24 UTC, Enjoys Math wrote:
>>> I have the following MWE:
>>>
>>> ```
>>> import std.exception;
>>> import std.stdio;
>>>
>>> abstract class B
>>> {
>>>    B opCall() {
>>>       throw new Exception("NotImplemented");
>>>    }
>>> }
>>>
>>> class A : B
>>> {
>>>    override B opCall() {
>>>       return new A();
>>>    }
>>> }
>>>
>>> int main() {
>>>    B a = new A();
>>>    a();
>>>    readln();
>>>    return 0;
>>> }
>>>
>>> ```
>>>
>>> But B.opCall() gets called!   I thought polymorphism was cool 
>>> until now....
>>>
>>> How can I get this to work the way I expected it to?  Would 
>>> an abstract method in base do it?
>>
>> Okay... now the MWE works as I expected polymorphism to work, 
>> but my complicated library is not doing it right...
>>
>> :\
>
> Here is a link to the library on github.  Please help me solve 
> this!! :D
>
> https://github.com/enjoysmath/diagram-chaser

Simply git clone it and run from main.d or hit debug in VisualD 
to see my problem.  It's calling the base class method which 
throws a NotImplemented exception, but it should be calling one 
of the derived subclasses.  I will keep coding on it and update 
the code, but if I get it fixed, I'll post an update here.