Charles Bournhonesque cbb4c26cad Enable deriving Reflect on structs with generic types (#7364) ... # Objective I recently had an issue, where I have a struct: ``` struct Property { inner: T } ``` that I use as a wrapper for internal purposes. I don't want to update my struct definition to ``` struct Property<T: Reflect>{ inner: T } ``` because I still want to be able to build `Property<T>` for types `T` that are not `Reflect`. (and also because I don't want to update my whole code base with `<T: Reflect>` bounds) I still wanted to have reflection on it (for `bevy_inspector_egui`), but adding `derive(Reflect)` fails with the error: `T cannot be sent between threads safely. T needs to implement Sync.` I believe that `bevy_reflect` should adopt the model of other derives in the case of generics, which is to add the `Reflect` implementation only if the generics also implement `Reflect`. (That is the behaviour of other macros such as `derive(Clone)` or `derive(Debug)`. It's also the current behavior of `derive(FromReflect)`. Basically doing something like: ``` impl<T> Reflect for Foo<T> where T: Reflect ``` ## Solution - I updated the derive macros for `Structs` and `TupleStructs` to add extra `where` bounds. - Every type that is reflected will need a `T: Reflect` bound - Ignored types will need a `T: 'static + Send + Sync` bound. Here's the reason. For cases like this: ``` #[derive(Reflect)] struct Foo<T, U>{ a: T #[reflect(ignore)] b: U } ``` I had to add the bound `'static + Send + Sync` to ignored generics like `U`. The reason is that we want `Foo<T, U>` to be `Reflect: 'static + Send + Sync`, so `Foo<T, U>` must be able to implement those auto-traits. `Foo<T, U>` will only implement those auto-traits if every generic type implements them, including ignored types. This means that the previously compile-fail case now compiles: ``` #[derive(Reflect)] struct Foo<'a> { #[reflect(ignore)] value: &'a str, } ``` But `Foo<'a>` will only be useable in the cases where `'a: 'static` and panic if we don't have `'a: 'static`, which is what we want (nice bonus from this PR ;) ) --- ## Changelog > This section is optional. If this was a trivial fix, or has no externally-visible impact, you can delete this section. ### Added Possibility to add `derive(Reflect)` to structs and enums that contain generic types, like so: ``` #[derive(Reflect)] struct Foo<T>{ a: T } ``` Reflection will only be available if the generic type T also implements `Reflect`. (previously, this would just return a compiler error)		2023-01-28 00:12:06 +00:00
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reflect_derive	Enable deriving Reflect on structs with generic types (#7364)	2023-01-28 00:12:06 +00:00
reflect_derive.rs	bevy_reflect: Add compile fail tests for bevy_reflect (#7041)	2023-01-02 21:07:33 +00:00