# Objective
- [`thiserror`](https://docs.rs/thiserror/) is used to derive the error
type on `bevy_dynamic_plugin`'s
[`DynamicPluginLoadError`](https://docs.rs/bevy_dynamic_plugin/latest/bevy_dynamic_plugin/enum.DynamicPluginLoadError.html).
- It is an enum where each variant wraps a `libloading` error type.
- `thiserror` supports marking this internal error types as `#[source]`
so it can automatically fill out the
[`Error::source`](https://doc.rust-lang.org/std/error/trait.Error.html#method.source)
method.
- This allows other error handling libraries to get more information
about the error than what Bevy by default provides. It increases
interoperability between libraries.
## Solution
- Mark the internal `libloading::Error` of `DynamicPluginLoadError` with
`#[source]`.
---
## Changelog
- Implemented the
[`Error::source`](https://doc.rust-lang.org/std/error/trait.Error.html#method.source)
method for
[`DynamicPluginLoadError`](https://docs.rs/bevy_dynamic_plugin/latest/bevy_dynamic_plugin/enum.DynamicPluginLoadError.html).
---
Here is the output from `cargo-expand` before and after the change.
```rust
// Before
impl Error for DynamicPluginLoadError {}
```
```rust
// After
impl Error for DynamicPluginLoadError {
fn source(&self) -> Option<&(dyn Error + 'static)> {
use thiserror::__private::AsDynError as _;
match self {
DynamicPluginLoadError::Library { 0: source, .. } => {
Some(source.as_dyn_error())
}
DynamicPluginLoadError::Plugin { 0: source, .. } => {
Some(source.as_dyn_error())
}
}
}
}
```
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