tardy v0.0.1 - Runtime polymorphism without inheritance

[Paul Backus]

On Tuesday, 16 June 2020 at 13:31:49 UTC, Atila Neves wrote:
>
> <snip>
>
> With a few changes, yes (added missing semicolons, changed 
> IGeometry to Geometry in `measure`, passed the current module 
> so tardy can find the UFCS functions, added `@safe pure` to the 
> UFCS functions:
>
[...]
>
> void main() {
>     auto r = Rect(3.0, 4.0);
>     auto c = Circle(5.0);
>
>     Geometry.create!__MODULE__(r).measure;
>     Geometry.create!__MODULE__(c).measure;
> }

IMO this can be done more elegantly by separating out the code 
that looks up methods in the current module from the code that 
does the actual type erasure.

A while ago, I collaborated briefly with Adam Kowalski from the 
Dlang discord server on some code to emulate C++-style 
argument-dependent lookup in D. Using that code, your example 
above would be written:

     Geometry.create(r.extended).measure;
     Geometry.create(c.extended).measure;

Here's a gist with the code, along with a small example:

https://gist.github.com/pbackus/0a70419eb8bece52f3a08edfe7b6019b

If anyone thinks it's worthwhile, I can toss this up on Dub. 
Personally, I've never had much use for it in my own projects.