I reiterate my comment from the pitch thread that because a computed property that cannot formally mutate the struct (one that either doesn't have a set or has a nonmutating set) is declared with var, and because property wrappers that similarly cannot mutate the struct are also declared var, it is most consistent for weak to be declared with var instead of let. I do agree that there is value in declaring a weak property or property wrapper's backing storage to be immutable, but it should be done another way (if the complexity in added syntax is a worthwhile tradeoff). The existing precedent is that a computed property/property wrapper is always declared with var even if it cannot mutate the backing storage, and we indicate that the backing storage is immutable not through let, but through the computed property either not having a set or having a nonmutating set.
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