type erased senders are not usable with repeat_effect_until, others?

[jessmorecroft]

Hi, I have a fairly broad sender graph I was building with various parts "hidden" behind exec::any_sender_of. It has just become apparent to me that because these type erased senders aren't copy constructible i can't use any of these senders, or senders composed of these senders, with certain adaptors that rely on copying, most notably at the moment, repeat_effect_until which does a copy on each connect. Hopefully I'm missing something here, or is this just an early adopter consequence/ pitfall of an evolving solution? Making all senders concrete is not a realistic option for me unfortunately.

[ericniebler]

thanks for the report. i'm pretty sure the repeat algorithms could support this by, instead of connecting a copy of the sender, connecting the sender equivalent of reference_wrapper. that is, write a sender_ref type that forwards the sender customization points to another sender held by reference, and then at each iteration, connecting a new sender_ref to the internal receiver.

if you are feeling inclined to contribute, please do.

[jessmorecroft]

Thanks @ericniebler i may have a crack at some point, but to be honest i think i need a lot more study of the code to be able to cobble something together. the implicit conventions and meta-programming are a bit beyond me at this point.