Direct setting of `current_task().scope` is undefined behaviour.

[vchuravy]

ProductionMonitoring.jl/src/Tracing/scoped_values_context.jl

Lines 31 to 42 in a278726

	function scoped_values_set_context(pair::Pair{<:ScopedValue}, rest::Pair{<:ScopedValue}...)
	ct = Base.current_task()
	original_scope = ct.scope::Union{Nothing, ScopedValues.Scope}
	ct.scope = ScopedValues.Scope(original_scope, pair, rest...)
	return original_scope
	end
	function scoped_values_reset_context(old)
	ct = current_task()
	ct.scope = old
	return nothing
	end

The direct modification of these fields is undefined behavior. JuliaLang/julia#52309

When I was asked about this in JuliaLang/ScopedValues.jl#14 (comment) I stated that this optimization was planned.

scope  = currrent_scope()
scoped_values_reset_context(#=...=#)
scope = current_scope()

Is now being transformed to:

scope  = currrent_scope()
scoped_values_reset_context(#=...=#)

The right way IMO is to "snapshot" the scope with a potential list of scoped values into a PersistentDict and then to write with(snapshot...) do f that sets those scopedvalues to those values again.

(found through Github search for ScopedValue)