Swift recursive enums not marked as indirect

Given a recursive message containing an oneof, generated Swift does not compile because enums are not marked with indirect keyword.

Proto:

message RecursiveMessage {
  oneof value {
    string value1 = 1;
    RecursiveMessage value2 = 2;
  }
}

Generated Swift:

public struct RecursiveMessage {

    public var value: Value?
    public var unknownFields: Data = .init()

    public init(value: Value? = nil) {
        self.value = value
    }

    public enum Value { /// ❌ Recursive enum 'RecursiveMesage.Value' is not marked 'indirect'

        case value1(String)
        case value2(RecursiveMessage)

        fileprivate func encode(to writer: ProtoWriter) throws {
            switch self {
            case .value1(let value1): try writer.encode(tag: 1, value: value1)
            case .value2(let value2): try writer.encode(tag: 2, value: value2)
            }
        }

    }

}

Marking case value2(RecursiveMessage) as indirect fixes the error.

A function for checking for reference cycles exists in the Swift generator here, however it does not seem to be used for enums. (per @JakeWharton).

Start in wire-swift-generator/src/main/java/com/squareup/wire/swift/SwiftGenerator.kt, especially the reference-cycle check around line 202 and enum generation around line 1372. Run the Swift generator tests that cover recursive messages, then verify that the shown RecursiveMessage proto generates Swift that compiles and that existing non-recursive enums remain unchanged.