XRTReal

[MikeInnes]

Flux also used to use TrackedScalar{T} = TrackedArray{T,0}, but it turns out 0D arrays are not treated consistently like scalars in a lot of places, and it's generally unhelpful for dispatch. Having a separate XRTReal <: Real object would simplify a lot of stuff (e.g. a lot more of Zygote would work for free), so it seems worth considering unless there's a specific reason not too.