bevy/crates/bevy_reflect/src/impls/smallvec.rs
PROMETHIA-27 c27a3cff6d Make Reflect safe to implement (#5010)
# Objective

Currently, `Reflect` is unsafe to implement because of a contract in which `any` and `any_mut` must return `self`, or `downcast` will cause UB. This PR makes `Reflect` safe, makes `downcast` not use unsafe, and eliminates this contract. 

## Solution

This PR adds a method to `Reflect`, `any`. It also renames the old `any` to `as_any`.
`any` now takes a `Box<Self>` and returns a `Box<dyn Any>`. 

---

## Changelog

### Added:
- `any()` method
- `represents()` method

### Changed:
- `Reflect` is now a safe trait
- `downcast()` is now safe
- The old `any` is now called `as_any`, and `any_mut` is now `as_mut_any`

## Migration Guide

- Reflect derives should not have to change anything
- Manual reflect impls will need to remove the `unsafe` keyword, add `any()` implementations, and rename the old `any` and `any_mut` to `as_any` and `as_mut_any`.
- Calls to `any`/`any_mut` must be changed to `as_any`/`as_mut_any`

## Points of discussion:

- Should renaming `any` be avoided and instead name the new method `any_box`?
- ~~Could there be a performance regression from avoiding the unsafe? I doubt it, but this change does seem to introduce redundant checks.~~
- ~~Could/should `is` and `type_id()` be implemented differently? For example, moving `is` onto `Reflect` as an `fn(&self, TypeId) -> bool`~~


Co-authored-by: PROMETHIA-27 <42193387+PROMETHIA-27@users.noreply.github.com>
2022-06-27 16:52:25 +00:00

142 lines
3.5 KiB
Rust

use smallvec::SmallVec;
use std::any::Any;
use crate::utility::GenericTypeInfoCell;
use crate::{
Array, ArrayIter, FromReflect, List, ListInfo, Reflect, ReflectMut, ReflectRef, TypeInfo, Typed,
};
impl<T: smallvec::Array + Send + Sync + 'static> Array for SmallVec<T>
where
T::Item: FromReflect + Clone,
{
fn get(&self, index: usize) -> Option<&dyn Reflect> {
if index < SmallVec::len(self) {
Some(&self[index] as &dyn Reflect)
} else {
None
}
}
fn get_mut(&mut self, index: usize) -> Option<&mut dyn Reflect> {
if index < SmallVec::len(self) {
Some(&mut self[index] as &mut dyn Reflect)
} else {
None
}
}
fn len(&self) -> usize {
<SmallVec<T>>::len(self)
}
fn iter(&self) -> ArrayIter {
ArrayIter {
array: self,
index: 0,
}
}
}
impl<T: smallvec::Array + Send + Sync + 'static> List for SmallVec<T>
where
T::Item: FromReflect + Clone,
{
fn push(&mut self, value: Box<dyn Reflect>) {
let value = value.take::<T::Item>().unwrap_or_else(|value| {
<T as smallvec::Array>::Item::from_reflect(&*value).unwrap_or_else(|| {
panic!(
"Attempted to push invalid value of type {}.",
value.type_name()
)
})
});
SmallVec::push(self, value);
}
}
impl<T: smallvec::Array + Send + Sync + 'static> Reflect for SmallVec<T>
where
T::Item: FromReflect + Clone,
{
fn type_name(&self) -> &str {
std::any::type_name::<Self>()
}
fn get_type_info(&self) -> &'static TypeInfo {
<Self as Typed>::type_info()
}
fn into_any(self: Box<Self>) -> Box<dyn Any> {
self
}
fn as_any(&self) -> &dyn Any {
self
}
fn as_any_mut(&mut self) -> &mut dyn Any {
self
}
fn as_reflect(&self) -> &dyn Reflect {
self
}
fn as_reflect_mut(&mut self) -> &mut dyn Reflect {
self
}
fn apply(&mut self, value: &dyn Reflect) {
crate::list_apply(self, value);
}
fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> {
*self = value.take()?;
Ok(())
}
fn reflect_ref(&self) -> ReflectRef {
ReflectRef::List(self)
}
fn reflect_mut(&mut self) -> ReflectMut {
ReflectMut::List(self)
}
fn clone_value(&self) -> Box<dyn Reflect> {
Box::new(List::clone_dynamic(self))
}
fn reflect_partial_eq(&self, value: &dyn Reflect) -> Option<bool> {
crate::list_partial_eq(self, value)
}
}
impl<T: smallvec::Array + Send + Sync + 'static> Typed for SmallVec<T>
where
T::Item: FromReflect + Clone,
{
fn type_info() -> &'static TypeInfo {
static CELL: GenericTypeInfoCell = GenericTypeInfoCell::new();
CELL.get_or_insert::<Self, _>(|| TypeInfo::List(ListInfo::new::<Self, T::Item>()))
}
}
impl<T: smallvec::Array + Send + Sync + 'static> FromReflect for SmallVec<T>
where
T::Item: FromReflect + Clone,
{
fn from_reflect(reflect: &dyn Reflect) -> Option<Self> {
if let ReflectRef::List(ref_list) = reflect.reflect_ref() {
let mut new_list = Self::with_capacity(ref_list.len());
for field in ref_list.iter() {
new_list.push(<T as smallvec::Array>::Item::from_reflect(field)?);
}
Some(new_list)
} else {
None
}
}
}