Deepcopy Fix

[willtebbutt]

Resolves #56775 . Credit for this fix rests entirely with @bbrehm .

I have a regression test -- see #56775 (comment) -- but I'm unsure where to put it. If someone could point me towards an appropriate location for the test, that would be very helpful!

edit: CC @nsajko

[LilithHafner]

Another option which registers the new copied item in the stackdict before recursing to the children is

function deepcopy_internal(x::Array{T, N}, stackdict::IdDict) where {T, N}
    if haskey(stackdict, x)
        return stackdict[x]::typeof(x)
    end
    y = stackdict[x] = Array{T, N}(undef, ntuple(Returns(0), Val{N}()))
    setfield!(y, :ref, deepcopy_internal(x.ref, stackdict))
    setfield!(y, :size, x.size)
    y
end

I'm worried about calling setfield! on an array, though. cc. @oscardssmith for weather that is okay in this context and also because #56775 was introduced by https://github.com/JuliaLang/julia/pull/51319/files#diff-471c7f0385825eae442274e0debe4e88fe50ce6898508130c9c14fbb7c29f255R119-R124

[LilithHafner]

If someone could point me towards an appropriate location for the test, that would be very helpful!

I'd put tests for this here:

julia/test/copy.jl

Line 255 in b58dcc5

[willtebbutt]

Another option which registers the new copied item in the stackdict before recursing to the children is

I'm happy to go with whichever is preferred -- I'll wait for @oscardssmith to weigh in before modifying.

[oscardssmith]

Calling setfield! on an array is fine (so long as you don't violate the invariant)

[willtebbutt]

Cool. I'll change the fix.

[willtebbutt]

Fix modified to following @LilithHafner 's suggestion, which I agree is probably cleaner. Test also fixed to actually be a test, rather than just evaluating a Bool.

[vtjnash]

Is this triggering a Revise.jl internal bug?

[willtebbutt]

It looks like the @eval statement I had (accidentally) left in the code was causing some kind of problem. The latest commit appears to resolve.

[willtebbutt]

It looks to me like the current test failures are unrelated to this PR, but someone who knows more about Julia's CI should probably take a look.