`construct_seeds` for types where `typeof(one(T)) !=T` is broken

[longemen3000]

as far as i understand, the type of one(T) is not necessarily T (JuliaPhysics/Measurements.jl#134 for example). but construct_seeds uses this:

ForwardDiff.jl/src/partials.jl

Lines 9 to 12 in 50ec9a1

	@generated function single_seed(::Type{Partials{N,V}}, ::Val{i}) where {N,V,i}
	ex = Expr(:tuple, [ifelse(i === j, :(one(V)), :(zero(V))) for j in 1:N]...)
	return :(Partials($(ex)))
	end

Maybe using oneunit there is more correct?

[stevengj]

If you want to get something of the same type, you should use oneunit, that's what it's for.

(e.g. for a dimensionful type, one must be dimensionless, i.e. of a different type, as otherwise it will not be a multiplicative identity.)