# Objective
The type `AssetLoadError` has `PartialEq` and `Eq` impls, which is
problematic due to the fact that the `AssetLoaderError` and
`AddAsyncError` variants lie in their impls: they will return `true` for
any `Box<dyn Error>` with the same `TypeId`, even if the actual value is
different. This can lead to subtle bugs if a user relies on the equality
comparison to ensure that two values are equal.
The same is true for `DependencyLoadState`,
`RecursiveDependencyLoadState`.
More generally, it is an anti-pattern for large error types involving
dynamic dispatch, such as `AssetLoadError`, to have equality
comparisons. Directly comparing two errors for equality is usually not
desired -- if some logic needs to branch based on the value of an error,
it is usually more correct to check for specific variants and inspect
their fields.
As far as I can tell, the only reason these errors have equality
comparisons is because the `LoadState` enum wraps `AssetLoadError` for
its `Failed` variant. This equality comparison is only used to check for
`== LoadState::Loaded`, which we can easily replace with an `is_loaded`
method.
## Solution
Remove the `{Partial}Eq` impls from `LoadState`, which also allows us to
remove it from the error types.
## Migration Guide
The types `bevy_asset::AssetLoadError` and `bevy_asset::LoadState` no
longer support equality comparisons. If you need to check for an asset's
load state, consider checking for a specific variant using
`LoadState::is_loaded` or the `matches!` macro. Similarly, consider
using the `matches!` macro to check for specific variants of the
`AssetLoadError` type if you need to inspect the value of an asset load
error in your code.
`DependencyLoadState` and `RecursiveDependencyLoadState` are not
released yet, so no migration needed,
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Co-authored-by: Joseph <21144246+JoJoJet@users.noreply.github.com>
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