adding loop_fn_back in to the future-rs

[warlord500]

I have created a small library that isn't entirely completed but almost there to add loop fn back in,
I wasn't entirely sure how I would alter the mod files to add it in but i think there

the library is at
https://github.com/warlord500/loop_fn_future

[ibraheemdev]

Quickly reviewing the implementation, you could use futures_core::ready instead of the macro yourself and pin-project-lite instead of get_unchecked_mut.

[taiki-e]

What is the use case for this?

Historically, this function has been removed in favor of loop + async/await. Looking at the previous discussion it could be useful in migrating from 0.1, but it's really temporary and I don't want to enable it by default.

In any case, I would like to know about specific use cases that require this.

[warlord500]

there nothing that requires this usage, my only thought is that it could be useful if you didn't want to write a future without using async and await for example purposes!

I certainly have no problem with it being under a feature flag for migration

[taiki-e]

I would prefer not to add this unless there is a specific use case that requires this.