Instantiate templated class at runtime

[Simen Kjærås]

On Sunday, 26 May 2019 at 17:51:37 UTC, Aphex wrote:
> 1. Is it possible to have a runtime class and struct creator 
> function that can deal with templates. It doesn't seem like it 
> should be that big a deal. One only needs to actually know the 
> size of class and that will depend on the template parameter 
> sizes, which if they are known then everything is known?

The root problem is described in 
https://issues.dlang.org/show_bug.cgi?id=2484. In short, the D 
runtime keeps track of all class types and lets you search 
through them and instantiate them if you wish. Sadly, this 
doesn't cover templated classes, in part because an instantiation 
of a templated class is not necessarily in the module that 
defined it, and because there may be multiple identical 
instantiations across multiple modules.

Now, templated classes still have .classinfo members, and these 
can be used with _d_newclass to create new instances of the 
class. I filed an issue with Orange for this: 
https://github.com/jacob-carlborg/orange/issues/57


> 2. Is the output or Orange for templated classes correct? 
> "Issue1.Y!string.Y" or should it be "Issue1.Y!string"? Else 
> this is a bug that I'll need to track down and fix.

The name Issue1.Y!string.Y is correct - 'class Y(T) {}' is short 
for 'template Y(T) { class Y {} }'.

--
   Simen