Julep: Efficient Hierarchical Mutable Data

[foobar_lv2]

Nice. However,

julia> f=BigForest(Elephant(1.0), Elephant(2.0), ""); f.elephant2.hunger
2.0

julia> typeof(f.elephant2)
ElephantView{:elephant2, BigForest}

julia> typeof(f.elephant2) == typeof(f.elephant1)
false

which brings up what I noted upthread:

@foobar_lv2

The thing that makes this a new language feature is the desire that typeof(fieldref(w::Whole, :part1)) === typeof(fieldref(w, :part2)), i.e. that the type does not imply the offsets from the parent object.

I think this would really require new (albeit simple) core intrinsics relating to GC write barriers and a very_unsafe_pointer_to_objref(typ::DataType, p::Ptr) = unsafe_pointer_to_objref(p)::typ that assumes the type instead of checking (so UB instead of exception if it’s wrong, unless check-bounds=yes, or some compiler flag for the julia runtime is set).