JoJoJet 05b498a224 Make the SystemParam derive macro more flexible (#6694) ... # Objective Currently, the `SystemParam` derive forces you to declare the lifetime parameters `<'w, 's>`, even if you don't use them. If you don't follow this structure, the error message is quite nasty. ### Example (before): ```rust #[derive(SystemParam)] pub struct EventWriter<'w, 's, E: Event> { events: ResMut<'w, Events<E>>, // The derive forces us to declare the `'s` lifetime even though we don't use it, // so we have to add this `PhantomData` to please rustc. #[system_param(ignore)] _marker: PhantomData<&'s ()>, } ``` ## Solution * Allow the user to omit either lifetime. * Emit a descriptive error if any lifetimes used are invalid. ### Example (after): ```rust #[derive(SystemParam)] pub struct EventWriter<'w, E: Event> { events: ResMut<'w, Events<E>>, } ``` --- ## Changelog * The `SystemParam` derive is now more flexible, allowing you to omit unused lifetime parameters.		2022-12-05 20:15:03 +00:00
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src	Make the SystemParam derive macro more flexible (#6694)	2022-12-05 20:15:03 +00:00
Cargo.toml	Release 0.9.0 (#6568)	2022-11-12 20:01:29 +00:00