mirror of
https://github.com/bevyengine/bevy
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245d03a78a
# Objective
Some of the new compile error messages are a little unclear (at least to
me). For example:
```
error[E0277]: `tests::foo::Bar` can not be created through reflection
--> crates/bevy_reflect/src/lib.rs:679:18
|
679 | #[derive(Reflect)]
| ^^^^^^^ the trait `from_reflect::FromReflect` is not implemented for `tests::foo::Bar`
|
= note: consider annotating `tests::foo::Bar` with `#[derive(Reflect)]` or `#[derive(FromReflect)]`
```
While the annotation makes it clear that `FromReflect` is missing, it's
not very clear from the main error message.
My IDE lists errors with only their message immediately present:
<p align="center">
<img width="700" alt="Image of said IDE listing errors with only their
message immediately present. These errors are as follows:
\"`tests::foo::Bar` can not be created through reflection\", \"The trait
bound `tests::foo::Bar: RegisterForReflection` is not satisfied\", and
\"The trait bound `tests::foo::Bar: type_info::MaybeTyped` is not
satisfied\""
src="https://github.com/user-attachments/assets/42c24051-9e8e-4555-8477-51a9407446aa">
</p>
This makes it hard to tell at a glance why my code isn't compiling.
## Solution
Updated all `on_unimplemented` attributes in `bevy_reflect` to mention
the relevant trait—either the actual trait or the one users actually
need to implement—as well as a small snippet of what not implementing
them means.
For example, failing to implement `TypePath` now mentions missing a
`TypePath` implementation. And failing to implement `DynamicTypePath`
now also mentions missing a `TypePath` implementation, since that's the
actual trait users need to implement (i.e. they shouldn't implement
`DynamicTypePath` directly).
Lastly, I also added some missing `on_unimplemented` attributes for
`MaybeTyped` and `RegisterForReflection` (which you can see in the image
above).
Here's how this looks in my IDE now:
<p align="center">
<img width="700" alt="Similar image as before showing the errors listed
by the IDE. This time the errors read as follows: \"`tests::foo::Bar`
does not implement `FromReflect` so cannot be reified through
reflection\", \"`tests::foo::Bar` does not implement
`GetTypeRegistration` so cannot be registered for reflection\", and
\"`tests::foo::Bar` does not implement `Typed` so cannot provide static
type information\""
src="https://github.com/user-attachments/assets/f6f8501f-0450-4f78-b84f-00e7a18d0533">
</p>
## Testing
You can test by adding the following code and verifying the compile
errors are correct:
```rust
#[derive(Reflect)]
struct Foo(Bar);
struct Bar;
```
|
||
|---|---|---|
| .. | ||
| src | ||
| tests | ||
| .gitignore | ||
| Cargo.toml | ||
| README.md | ||
Compile fail tests for bevy_reflect
This crate is separate from bevy_reflect and not part of the Bevy workspace in order to not fail crater tests for
Bevy.
The tests assert on the exact compiler errors and can easily fail for new Rust versions due to updated compiler errors (e.g. changes in spans).
The CI workflow executes these tests on the stable rust toolchain (see tools/ci).
For information on writing tests see compile_fail_utils/README.md.