Require main actor isolation in store collection (#3333)

* Require main actor isolation in store collection

* `preconditionIsolated` is not available in iOS <14

* Update Sources/ComposableArchitecture/Observation/IdentifiedArray+Observation.swift

Sources/ComposableArchitecture/Observation/IdentifiedArray+Observation.swift

@@ -90,6 +90,11 @@
  private let store: Store<IdentifiedArray<ID, State>, IdentifiedAction<ID, Action>>
  private let data: IdentifiedArray<ID, State>
 
+ #if swift(<5.10)
+ @MainActor(unsafe)
+ #else
+ @preconcurrency@MainActor
+ #endif
  fileprivate init(_ store: Store<IdentifiedArray<ID, State>, IdentifiedAction<ID, Action>>) {
  self.store = store
  self.data = store.withState { $0 }
@@ -98,21 +103,35 @@
  public var startIndex: Int { self.data.startIndex }
  public var endIndex: Int { self.data.endIndex }
  public subscript(position: Int) -> Store<State, Action> {
- guard self.data.indices.contains(position)
- else {
- return Store()
- }
- let id = self.data.ids[position]
- var element = self.data[position]
- return self.store.scope(
- id: self.store.id(state: \.[id:id]!, action: \.[id:id]),
- state: ToState {
- element = $0[id: id] ?? element
- return element
- },
- action: { .element(id: id, action: $0) },
- isInvalid: { !$0.ids.contains(id) }
+ precondition(
+ Thread.isMainThread,
+ #"""
+ Store collections must be interacted with on the main actor.
+
+ When passing a scoped store to a 'ForEach' in a lazy view (for example, 'LazyVStack'), it \
+ must be eagerly transformed into a collection to avoid access off the main actor:
+
+ Array(store.scope(state: \.elements, action: \.elements))
+ """#
  )
+ return MainActor._assumeIsolated { [uncheckedSelf = UncheckedSendable(self)] in
+ let `self` = uncheckedSelf.wrappedValue
+ guard self.data.indices.contains(position)
+ else {
+ return Store()
+ }
+ let id = self.data.ids[position]
+ var element = self.data[position]
+ return self.store.scope(
+ id: self.store.id(state: \.[id:id]!, action: \.[id:id]),
+ state: ToState {
+ element = $0[id: id] ?? element
+ return element
+ },
+ action: { .element(id: id, action: $0) },
+ isInvalid: { !$0.ids.contains(id) }
+ )
+ }
  }
  }
 #endif