[RFC/ANN] Restacker.jl: A workaround for the heap-allocated-immutable problem?

[jzr]

Does https://github.com/JuliaLang/julia/pull/42465 solve the problems listed in this thread?

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Edit: @foobar_lv2 are your issues from Immutables with reference-fields: Why boxed? - #19 by foobar_lv2 solved?