
# Objective Currently, reflecting a generic type provides no information about the generic parameters. This means that you can't get access to the type of `T` in `Foo<T>` without creating custom type data (we do this for [`ReflectHandle`](https://docs.rs/bevy/0.14.2/bevy/asset/struct.ReflectHandle.html#method.asset_type_id)). ## Solution This PR makes it so that generic type parameters and generic const parameters are tracked in a `Generics` struct stored on the `TypeInfo` for a type. For example, `struct Foo<T, const N: usize>` will store `T` and `N` as a `TypeParamInfo` and `ConstParamInfo`, respectively. The stored information includes: - The name of the generic parameter (i.e. `T`, `N`, etc.) - The type of the generic parameter (remember that we're dealing with monomorphized types, so this will actually be a concrete type) - The default type/value, if any (e.g. `f32` in `T = f32` or `10` in `const N: usize = 10`) ### Caveats The only requirement for this to work is that the user does not opt-out of the automatic `TypePath` derive with `#[reflect(type_path = false)]`. Doing so prevents the macro code from 100% knowing that the generic type implements `TypePath`. This in turn means the generated `Typed` impl can't add generics to the type. There are two solutions for this—both of which I think we should explore in a future PR: 1. We could just not use `TypePath`. This would mean that we can't store the `Type` of the generic, but we can at least store the `TypeId`. 2. We could provide a way to opt out of the automatic `Typed` derive with a `#[reflect(typed = false)]` attribute. This would allow users to manually implement `Typed` to add whatever generic information they need (e.g. skipping a parameter that can't implement `TypePath` while the rest can). I originally thought about making `Generics` an enum with `Generic`, `NonGeneric`, and `Unavailable` variants to signify whether there are generics, no generics, or generics that cannot be added due to opting out of `TypePath`. I ultimately decided against this as I think it adds a bit too much complexity for such an uncommon problem. Additionally, user's don't necessarily _have_ to know the generics of a type, so just skipping them should generally be fine for now. ## Testing You can test locally by running: ``` cargo test --package bevy_reflect ``` --- ## Showcase You can now access generic parameters via `TypeInfo`! ```rust #[derive(Reflect)] struct MyStruct<T, const N: usize>([T; N]); let generics = MyStruct::<f32, 10>::type_info().generics(); // Get by index: let t = generics.get(0).unwrap(); assert_eq!(t.name(), "T"); assert!(t.ty().is::<f32>()); assert!(!t.is_const()); // Or by name: let n = generics.get_named("N").unwrap(); assert_eq!(n.name(), "N"); assert!(n.ty().is::<usize>()); assert!(n.is_const()); ``` You can even access parameter defaults: ```rust #[derive(Reflect)] struct MyStruct<T = String, const N: usize = 10>([T; N]); let generics = MyStruct::<f32, 5>::type_info().generics(); let GenericInfo::Type(info) = generics.get_named("T").unwrap() else { panic!("expected a type parameter"); }; let default = info.default().unwrap(); assert!(default.is::<String>()); let GenericInfo::Const(info) = generics.get_named("N").unwrap() else { panic!("expected a const parameter"); }; let default = info.default().unwrap(); assert_eq!(default.downcast_ref::<usize>().unwrap(), &10); ```
227 lines
6.2 KiB
Rust
227 lines
6.2 KiB
Rust
use bevy_reflect_derive::impl_type_path;
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use smallvec::{Array as SmallArray, SmallVec};
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use core::any::Any;
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use crate::{
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self as bevy_reflect, utility::GenericTypeInfoCell, ApplyError, FromReflect, FromType,
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Generics, GetTypeRegistration, List, ListInfo, ListIter, MaybeTyped, PartialReflect, Reflect,
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ReflectFromPtr, ReflectKind, ReflectMut, ReflectOwned, ReflectRef, TypeInfo, TypeParamInfo,
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TypePath, TypeRegistration, Typed,
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};
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impl<T: SmallArray + TypePath + Send + Sync> List for SmallVec<T>
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where
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T::Item: FromReflect + MaybeTyped + TypePath,
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{
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fn get(&self, index: usize) -> Option<&dyn PartialReflect> {
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if index < SmallVec::len(self) {
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Some(&self[index] as &dyn PartialReflect)
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} else {
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None
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}
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}
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fn get_mut(&mut self, index: usize) -> Option<&mut dyn PartialReflect> {
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if index < SmallVec::len(self) {
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Some(&mut self[index] as &mut dyn PartialReflect)
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} else {
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None
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}
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}
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fn insert(&mut self, index: usize, value: Box<dyn PartialReflect>) {
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let value = value.try_take::<T::Item>().unwrap_or_else(|value| {
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<T as SmallArray>::Item::from_reflect(&*value).unwrap_or_else(|| {
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panic!(
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"Attempted to insert invalid value of type {}.",
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value.reflect_type_path()
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)
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})
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});
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SmallVec::insert(self, index, value);
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}
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fn remove(&mut self, index: usize) -> Box<dyn PartialReflect> {
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Box::new(self.remove(index))
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}
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fn push(&mut self, value: Box<dyn PartialReflect>) {
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let value = value.try_take::<T::Item>().unwrap_or_else(|value| {
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<T as SmallArray>::Item::from_reflect(&*value).unwrap_or_else(|| {
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panic!(
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"Attempted to push invalid value of type {}.",
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value.reflect_type_path()
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)
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})
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});
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SmallVec::push(self, value);
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}
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fn pop(&mut self) -> Option<Box<dyn PartialReflect>> {
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self.pop()
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.map(|value| Box::new(value) as Box<dyn PartialReflect>)
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}
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fn len(&self) -> usize {
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<SmallVec<T>>::len(self)
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}
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fn iter(&self) -> ListIter {
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ListIter::new(self)
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}
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fn drain(&mut self) -> Vec<Box<dyn PartialReflect>> {
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self.drain(..)
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.map(|value| Box::new(value) as Box<dyn PartialReflect>)
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.collect()
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}
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}
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impl<T: SmallArray + TypePath + Send + Sync> PartialReflect for SmallVec<T>
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where
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T::Item: FromReflect + MaybeTyped + TypePath,
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{
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fn get_represented_type_info(&self) -> Option<&'static TypeInfo> {
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Some(<Self as Typed>::type_info())
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}
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#[inline]
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fn into_partial_reflect(self: Box<Self>) -> Box<dyn PartialReflect> {
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self
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}
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fn as_partial_reflect(&self) -> &dyn PartialReflect {
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self
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}
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fn as_partial_reflect_mut(&mut self) -> &mut dyn PartialReflect {
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self
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}
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fn try_into_reflect(self: Box<Self>) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>> {
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Ok(self)
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}
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fn try_as_reflect(&self) -> Option<&dyn Reflect> {
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Some(self)
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}
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fn try_as_reflect_mut(&mut self) -> Option<&mut dyn Reflect> {
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Some(self)
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}
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fn apply(&mut self, value: &dyn PartialReflect) {
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crate::list_apply(self, value);
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}
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fn try_apply(&mut self, value: &dyn PartialReflect) -> Result<(), ApplyError> {
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crate::list_try_apply(self, value)
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}
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fn reflect_kind(&self) -> ReflectKind {
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ReflectKind::List
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}
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fn reflect_ref(&self) -> ReflectRef {
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ReflectRef::List(self)
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}
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fn reflect_mut(&mut self) -> ReflectMut {
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ReflectMut::List(self)
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}
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fn reflect_owned(self: Box<Self>) -> ReflectOwned {
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ReflectOwned::List(self)
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}
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fn clone_value(&self) -> Box<dyn PartialReflect> {
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Box::new(self.clone_dynamic())
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}
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fn reflect_partial_eq(&self, value: &dyn PartialReflect) -> Option<bool> {
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crate::list_partial_eq(self, value)
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}
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}
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impl<T: SmallArray + TypePath + Send + Sync> Reflect for SmallVec<T>
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where
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T::Item: FromReflect + MaybeTyped + TypePath,
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{
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fn into_any(self: Box<Self>) -> Box<dyn Any> {
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self
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}
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fn as_any(&self) -> &dyn Any {
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self
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}
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fn as_any_mut(&mut self) -> &mut dyn Any {
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self
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}
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fn into_reflect(self: Box<Self>) -> Box<dyn Reflect> {
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self
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}
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fn as_reflect(&self) -> &dyn Reflect {
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self
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}
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fn as_reflect_mut(&mut self) -> &mut dyn Reflect {
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self
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}
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fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> {
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*self = value.take()?;
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Ok(())
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}
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}
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impl<T: SmallArray + TypePath + Send + Sync + 'static> Typed for SmallVec<T>
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where
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T::Item: FromReflect + MaybeTyped + TypePath,
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{
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fn type_info() -> &'static TypeInfo {
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static CELL: GenericTypeInfoCell = GenericTypeInfoCell::new();
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CELL.get_or_insert::<Self, _>(|| {
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TypeInfo::List(
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ListInfo::new::<Self, T::Item>()
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.with_generics(Generics::from_iter([TypeParamInfo::new::<T>("T")])),
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)
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})
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}
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}
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impl_type_path!(::smallvec::SmallVec<T: SmallArray>);
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impl<T: SmallArray + TypePath + Send + Sync> FromReflect for SmallVec<T>
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where
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T::Item: FromReflect + MaybeTyped + TypePath,
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{
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fn from_reflect(reflect: &dyn PartialReflect) -> Option<Self> {
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let ref_list = reflect.reflect_ref().as_list().ok()?;
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let mut new_list = Self::with_capacity(ref_list.len());
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for field in ref_list.iter() {
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new_list.push(<T as SmallArray>::Item::from_reflect(field)?);
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}
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Some(new_list)
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}
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}
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impl<T: SmallArray + TypePath + Send + Sync> GetTypeRegistration for SmallVec<T>
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where
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T::Item: FromReflect + MaybeTyped + TypePath,
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{
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fn get_type_registration() -> TypeRegistration {
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let mut registration = TypeRegistration::of::<SmallVec<T>>();
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registration.insert::<ReflectFromPtr>(FromType::<SmallVec<T>>::from_type());
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registration
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}
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}
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#[cfg(feature = "functions")]
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crate::func::macros::impl_function_traits!(SmallVec<T>; <T: SmallArray + TypePath + Send + Sync> where T::Item: FromReflect + MaybeTyped + TypePath);
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