Interference with Distributed.jl on Windows

Following some detective work with the help of @rikhuijzer and @ChrisRackauckas on https://discourse.julialang.org/t/github-action-mysteriously-starts-breaking-on-windows/86048, it seems as though ReverseDiff.jl is interfering with Distributed.jl and causing some issues.

When I import ReverseDiff.jl into SymbolicRegression.jl (either directly, or if it is imported in a dependency of a dependency) the unit tests on Windows break. These unit tests use Distributed.jl to dynamically allocate worker processes. No other operating systems are affected.

This bug can reproduced with the following code, which dynamically allocates some worker processes, activates the current environment on each, and then imports ReverseDiff.jl on each.

using Pkg
using Distributed
import ReverseDiff
procs = addprocs(4)

# Activate env on workers:
project_path = splitdir(Pkg.project().path)[1]
@everywhere procs begin
    Base.MainInclude.eval(
        quote
            using Pkg
            Pkg.activate($$project_path)
        end,
    )
end

# Import package on workers:
@everywhere procs begin
    Base.MainInclude.eval(import ReverseDiff)
end

This code will work on Ubuntu and macOS, and works for every other package I've tested it on (all the dependencies of SymbolicRegression.jl are loaded this way). It is just the combination of Windows + ReverseDiff.jl that produce an error for some weird reason. You can see the error log here: https://github.com/MilesCranmer/SymbolicRegression.jl/runs/7943853737?check_suite_focus=true#step:6:232.

I really have no idea what could be causing this. Any clue? Does ReverseDiff.jl change any core functions in any way that would impact this?

Thanks!
Miles

Start with the supplied Windows reproduction using Distributed.addprocs, Pkg.activate, and @everywhere import ReverseDiff, then compare it with Ubuntu and macOS. Inspect the linked GitHub Actions error log for the first failure and determine whether importing ReverseDiff causes it; done means the worker setup and affected Windows tests pass without breaking other platforms.