FyroxEngine/Fyrox · critical

Type mismatch!

Error message

Type mismatch!

What it means

ResourceDataRef::deref casts the internally stored resource data (as &dyn Any) down to the requested type T and panics if the cast fails. This means the concrete Resource<T> handle being dereferenced does not actually hold data of type T — a programming/type confusion bug, not a load failure.

Solutions

1. Check the resource's actual type before dereferencing (e.g. untyped.procedural_data_source / instance_id type, or use UntypedResource::try_cast::<T>() and handle None).
2. Ensure the Resource<T> handle came from the correctly typed load call (resource_manager.request::<Model, _>(path) etc.).
3. In generic code, use downcast_ref::<T>() manually with a graceful error instead of blindly dereferencing.

Example fix

// before
let model: UntypedResource = ...;
let data = model.try_cast::<Texture>().unwrap();
let tex = data.data_ref(); // panics: actually a Model
// after
if let Some(tex_res) = model.try_cast::<Texture>() {
    let tex = tex_res.data_ref();
} else {
    Log::err("Resource is not a Texture");
}

if untyped.try_cast::<T>().is_none() {
    // handle wrong-typed resource before calling data_ref()
}

fn is_of_type<T: ResourceData>(r: &UntypedResource) -> bool { r.try_cast::<T>().is_some() }

When it happens

Trigger: Dereferencing a Resource<T> whose handle was produced from a differently-typed resource (e.g. via UntypedResource::try_cast or clone of a resource of another type), or after unsafely mixing typed/untyped resource APIs.

Common situations: Casting an UntypedResource to the wrong model type and calling data_ref(); passing a Texture where a Model is expected; generic code that lost the concrete type of the resource.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Cast to failed!
• Cast to failed!
• Resource type mismatch. Expected
• Unable to get a resource of type
• Unable to get a resource of type

AI-assisted analysis of FyroxEngine/Fyrox@76c91aad8e (2026-09-10). Data as JSON: /api/errors/ede2d49d21f55759. Report an issue: GitHub.

Appendix: source

Thrown at fyrox-resource/src/lib.rs:623

                panic!(
                    "Attempt to get reference to resource data while it is loading! Type {}",
                    std::any::type_name::<T>()
                )
            }
            ResourceState::LoadError {
                ref path,
                ref error,
            } => {
                let path = if path.as_os_str().is_empty() {
                    "Unknown".to_string()
                } else {
                    format!("{path:?}")
                };
                panic!("Attempt to get reference to resource data which failed to load! Type {}. Path: {path}. Error: {error:?}", std::any::type_name::<T>())
            }
            ResourceState::Ok { ref data } => (data.inner_ref() as &dyn Any)
                .downcast_ref()
                .expect("Type mismatch!"),
        }
    }
}

impl<T> DerefMut for ResourceDataRef<'_, T>
where
    T: TypedResourceData,
{
    fn deref_mut(&mut self) -> &mut Self::Target {
        let header = &mut *self.guard;
        match header.state {
            ResourceState::Unloaded => {
                panic!("Attempt to get reference to resource data while it is unloaded!")
            }
            ResourceState::Pending { .. } => {
                panic!("Attempt to get reference to resource data while it is loading!")
            }
            ResourceState::LoadError { .. } => {

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