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(Note: #15434 implements something very similar to this for functional curve adaptors, which is why they aren't present in this PR.) # Objective Previously, there was basically no chance that the explicitly-interpolating sample curve structs from the `Curve` API would actually be `Reflect`. The reason for this is functional programming: the structs contain an explicit interpolation `I: Fn(&T, &T, f32) -> T` which, under typical circumstances, will never be `Reflect`, which prevents the derive from realistically succeeding. In fact, they won't be a lot of other things either, notably including both`Debug` and `TypePath`, which are also required for reflection to succeed. The goal of this PR is to weaken the implementations of reflection traits for these structs so that they can implement `Reflect` under reasonable circumstances. (Notably, they will still not be `FromReflect`, which is unavoidable.) ## Solution The function fields are marked as `#[reflect(ignore)]`, and the derive macro for `Reflect` has `FromReflect` disabled. (This is not fully optimal, but we don't presently have any kind of "read-only" attribute for these fields.) Additionally, these structs receive custom `Debug` and `TypePath` implementations that display the function's (unstable!) type name instead of its value or type path (respectively). In the case of `TypePath`, this is a bit janky, but the instability of `type_name` won't generally present an issue for generics, which would have to be registered manually in the type registry anyway, which is impossible because the function type parameters cannot be named. (And in general, the "blessed" route for such cases would generally involve manually monomorphizing the function parameter away, which also allows access to `FromReflect` etc. through very ordinary use of the derive macro.) ## Testing Tests in the new `bevy_math::curve::sample_curves` module guarantee that these are actually `Reflect` under reasonable circumstances. --- ## Future changes If and when function item types become `Default`, these types will need to receive custom `FromReflect` implementations that exploit it. Such a custom implementation would also be desirable if users start doing things like wrapping function items in `Default`/`FromReflect` wrappers that still implement a `Fn` trait. Additionally, if function types become nameable in user-space, the stance on `Debug`/`TypePath` may bear reexamination, since partial monomorphization through wrappers would make implementing reflect traits for function types potentially more viable. --------- Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com> |
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Bevy Math
