Is there any practical benefit of tracing Val?

[avik-pal]

Base.@nospecializeinfer function traced_type_inner(
    @nospecialize(VT::Type{<:Val}),
    seen,
    @nospecialize(mode::TraceMode),
    @nospecialize(track_numbers::Type)
)
    if VT isa UnionAll
        return VT
    end
    T = VT.parameters[1]
    if traced_type_inner(typeof(T), seen, mode, track_numbers) == typeof(T)
        return Val{T}
    end
    throw("Val type $(Val{T}) cannot be traced")
end

When we construct while/if we need to track_numbers which in-turn tries to trace through Val (which occurs very commonly inside Lux states), and this eventually errors. If there is no practical applicability, can we remove this?

[wsmoses]

I think it is impossible to use a Val of a traced.

So the question is whether it is helpful to error (eg someone trying to move something through a Val they would’ve expected or error early, or just to fast path return as is

[avik-pal]

Maybe a warning and proceed? Since users can't disable this it makes doing things like

st = (; a = 1, training = Val(true))

Reactant.to_rarray(st; track_numbers=Number)

I would expect a to be tracked and training be left as is.