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# [derive(Clone)] Is Broken

(rgbcu.be)
128 points RGBCube | 2 comments | 04 Jul 25 20:31 UTC | HN request time: 0.001s | source
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lidavidm ◴[08 Jul 25 07:05 UTC] No.44497766[source]▶
Someone on the issue they made explained why Clone is "broken": https://github.com/JelteF/derive_more/issues/490#issuecommen...

Which links to this blog post explaining the choice in more detail: https://smallcultfollowing.com/babysteps/blog/2022/04/12/imp...

replies(3): >>44497807 #>>44497874 #>>44498301 #
1. samsartor ◴[08 Jul 25 08:58 UTC] No.44498301[source]▶
I have a crate with a "perfect" derive macro that generates where clauses from the fields instead of putting them on the generic parameters. It is nice when it works, but yah cyclical trait matching is still a real problem. I wound up needing an attribute to manually override the bounds whenever they blow up: https://docs.rs/inpt/latest/inpt/#bounds
replies(1): >>44500154 #
2. mmastrac ◴[08 Jul 25 14:09 UTC] No.44500154[source]▶
I did a similar thing for derive-io. It greatly improved the ergonomics of the macro.

https://docs.rs/derive-io/latest/derive_io/

Being able to handle directly recursive type bounds would be an awesome improvement to the compiler, IMO.