Let's get the semantic around closure fixed.

[Adam D. Ruppe]

On Thursday, 20 May 2021 at 11:40:24 UTC, Ola Fosheim Grostad 
wrote:
> But delegates have to work without a GC too

Well they do... sort of.

You can always take the address of a struct member function and 
now you have your nogc delegate.

Of course the difficulty is the receiving function has no way to 
knowing if that void* it received is a struct or an automatically 
captured variable set or what.

And the capture list takes a little work but there's tricks like 
making it all in a struct.

I wrote about this not too long ago:
http://dpldocs.info/this-week-in-d/Blog.Posted_2021_03_01.html#tip-of-the-week


However the delegate itself is less useful than a functor or 
interface though unless you must pass it to existing code. And 
then unless it is a `scope` receiver you're asking for a leak 
anyway again because of that void* being unknown to the caller 
(which is why this is possible at all, but also it leaves you a 
bit stuck).


It would be kinda cool if the compiler would magically pack small 
types into that void* sometimes. Since it is opaque to the caller 
it could actually pack in a captured int or two right there and 
be a by-value delegate.