Naga Error Message Is Cryptic on Missing Specifier in Struct

[OptimisticPeach]

Description
I'm trying to extend bevy's shaders, and I need to pass an extra value from vertex to fragment. Bevy has a few functions available which take the original VertexOutput struct as a parameter. Therefore, I decided that introducing this struct would be reasonable:

struct ActualOut {
    inner: VertexOutput, // original bevy struct
    @location(8) view_position: vec3<f32>,
}

And then replaced the input/output types of my vertex/fragment shaders with ActualOut. Unfortunately, Naga complains about the inner field lacking an @location marker -- I'm not sure if this is actually incorrect according to the spec, however in any case if it is indeed the intended behaviour then the error is massively cryptic:

2024-12-30T07:32:15.713303Z ERROR wgpu_core::device::global: Device::create_shader_module error:
Shader validation error: Entry point fragment at Fragment is invalid
  ┌─ :1:1
  │
1 │
  │   naga::Type [56]
  │
  = Argument 0 varying error
  = Struct member 0 is missing a binding

I'm running on naga v23.1.0.

If you need more details (a repro isn't super easy to put together, but if you need me to I'd be happy to do so), please let me know.

[sagudev]

This is not allowed per spec:

struct B {
  @location(0) x: f32
}

struct C {
  // Invalid, structures with user-defined IO cannot be nested.
  b: B
}