Why Swift Testing require execution in MainActor? [duplicate]

I'm trying to migrate over to the Swift 6 language mode, but the biggest issue I'm facing is that any use of SwiftData #Predicate or SortDescriptor results in this warning from the compiler:

Type 'ReferenceWritableKeyPath<GuruSchemaV2.Rubric, Bool>' does not conform to the 'Sendable' protocol; this is an error in the Swift 6 language mode

Here is an example predicate, from a static method on the Rubric type:

static func notArchived() -> Predicate<Rubric> { return #Predicate<Rubric> { rubric in !rubric.archived } }

And the error highlights line 5 of the expanded macro:

Foundation.Predicate<Rubric>({ rubric in PredicateExpressions.build_Negation( PredicateExpressions.build_KeyPath( root: PredicateExpressions.build_Arg(rubric), keyPath: \.archived // <- Warning here ) ) })

What is the correct way to reference properties of a model type using #Predicate?

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Edit: Rubric is a large class but here is the declaration and relevant properties:

@Model class Rubric: Identifiable, Comparable { init() { ... } var subject: String = "" var unit: String = "" var archived: Bool = false // ... }