BindingAction.set support for optional-chained KeyPath

[andreyz]

I have a UserState that contains optional SettingsState. In SettingsState isPresented property triggers SwiftUI view dismissal.

struct UserState {
  var settings: SettingsState?
  ...
}
struct SettingsState {
  var isPresented: Bool
  ...
}

If I'd like to execute an action that dismissed the SettingsView if it's state is non-nil from the userReducer, I could send an action like .binding(.set(\.settings?.isPresented, false)), but here Swift complains that it expects a WritableKeyPath, which is cased by SR-5820: Optional-chained KeyPath not Writable.

As Joe Groff points out in the above mentioned SR-5820, it's possible to compose key paths as follows

x?[keyPath: fooKeyPath] = 1 // no-op if x == nil, otherwise assign x!.foo = 1

How would one go about introducing an extension to BindingAction that would allow to write to a potentially nil root value?
I have a hunch that writing an extension to BindingAction.set could solve it, but I can't get past making Root conform to Optional here... As well as BindingAction.init being private.

public static func set<Value>(
    _ keyPath: WritableKeyPath<Root, Value>,
    _ value: Value
  ) -> Self
  where Value: Equatable {
    .init(
      keyPath: keyPath,
      set: { $0?[keyPath: keyPath] = value },
      value: value,
      valueIsEqualTo: { $0 as? Value == value }
    )
  }