Difficulty Serializing Vec<Box<dyn Reflect>>

[pop]

I am attempting to serialize and de-serialize a list of many different types of events (think tracking and playing back input events).

Unfortunately I have hit a roadblock with Bevy not liking my data structure for storing events: Vec<Box<dyn Reflect>>.
Below is a minimal repro to get the compiler error:

use bevy::prelude::*;

#[derive(Reflect, Default)]
struct Foo {
    things: Vec<Box<dyn Reflect>>,
}

fn main() {
    let a = Foo::default().as_reflect();
}

This gets the following compiler error with bevy = "0.16.0" and rustc 1.89.0-nightly (4d051fb30 2025-05-18):

Long compiler output...

   Compiling bevy_vcr v0.1.0 (/home/pop/Projects/src/localhost/angling-ground/bevy_vcr)
error[E0599]: the method `as_reflect` exists for struct `Foo`, but its trait bounds were not satisfied
   --> examples/reflect.rs:14:28
    |
9   | struct Foo {
    | ---------- method `as_reflect` not found for this struct because it doesn't satisfy `Foo: bevy::prelude::Reflect`
...
14  |     let a = Foo::default().as_reflect();
    |                            ^^^^^^^^^^ method cannot be called on `Foo` due to unsatisfied trait bounds
    |
   ::: /nix/store/sl37pbg8g9h30h0y3v072lkdrnyz4kjf-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:409:1
    |
409 | pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global> {
    | ------------------------------------------------------------------------------------------------ doesn't satisfy `_: FromReflect`, `_: MaybeTyped`, `_: RegisterForReflection` or `_: TypePath`
    |
    = note: the following trait bounds were not satisfied:
            `std::vec::Vec<std::boxed::Box<(dyn bevy::prelude::Reflect + 'static)>>: FromReflect`
            `std::vec::Vec<std::boxed::Box<(dyn bevy::prelude::Reflect + 'static)>>: MaybeTyped`
            `std::vec::Vec<std::boxed::Box<(dyn bevy::prelude::Reflect + 'static)>>: RegisterForReflection`
            `std::vec::Vec<std::boxed::Box<(dyn bevy::prelude::Reflect + 'static)>>: TypePath`
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `as_reflect`, perhaps you need to implement it:
            candidate #1: `bevy::prelude::Reflect`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `bevy_vcr` (example "reflect") due to 1 previous error

I am able to write events to this list just fine using .into_reflect() but when trying to serialize events out I get the above compiler error.

Anybody know what I might be doing wrong? Is this possible in Bevy today? If so what do I need to change about my usage?

[MrGVSV]

Unfortunately not possible today. You could maybe get around it by using Arc<dyn Reflect>, assuming the types all register ReflectSerialize, but it's still an in-progress feature.

We currently need this PR (which I’m planning to rebase), as well as some additional stuff I’m currently working on. I’m hopeful we can get this functionality in 0.17 though so stay tuned!