Storing interfaces as void[]

[tsbockman]

On Saturday, 13 March 2021 at 15:44:53 UTC, frame wrote:
> Maybe I don't get this right but why you don't just use the 
> void[] as it is?
>
> void[] mem = [i];
> //...
> return (cast(T[]) mem)[0];
>
> This is how I exchange variable data between DLLs.

That works, and is more elegant than the OP's solution. (And, I 
didn't know you could do it that way, so thanks for sharing!)

However, it still adds an unnecessary second level of indirection 
for interfaces and classes. The simplest and most efficient 
solution is actually this:

     auto indirect = cast(void*) i; // i is of type I.
     // ...
     return cast(I) indirect;

Where `is(I : T*, T) || is(I == interface) || is(I == class)`. 
The constraint enforces that all types should be accessed through 
exactly one level of indirection, allowing the same code to 
handle both reference types and value types with maximum 
efficiency.