mutable struct Node{N, T, D<:Data{N,T}}
center::SVector{N,T}
p::Union{D, Nothing}
child::Union{Array{Node{N,T},1}, Nothing}
end
might be what you want.
mutable struct Node{N, T, D<:Data{N,T}}
center::SVector{N,T}
p::Union{D, Nothing}
child::Union{Array{Node{N,T},1}, Nothing}
end
might be what you want.