Core Data: SortDescriptor based on first in to-many relationship

Question

I have an entity A that has an ordered to-many relationship to another entity B.

I'd like to sort a fetchrequest for A by a property (name) of the first (if available) B.

For example, I have

• A1 that is related to B.name = "Alice" and B.name = "Bob" and
• A2 that is related to B.name = "Eve"

Now I want to build a SortDescriptor that orders them by the name of the first B, i.e. A1, A2

Intuitively, I'd try to use

SortDescriptor(\A.relationship?.firstObject?.name)

but that doesn't compile (Failed to produce diagnostic for expression;).

Is this simply not possible or am I missing something?