.swifinterface undeclared generic types


I'm trying to extract some of our internal modules to external modules, compiled and distributed as xcframeworks. I'm struggling right now linking back the new xcframework back to the app.

When I compile the application with the new dependency added, I get several errors in the generated swiftinterface.

The original code (the library to be extracted) contains among many other things, an extension on Swift.Result:

public extension Swift.Result {
  typealias Callback = (_ result: Swift.Result<Success, Failure>) -> Void

  init(value: Success) {
    self = .success(value)
  init(error: Failure) {
    self = .failure(error)

  var value: Success? {
    return try? self.get()


Where Success and Failure are defined as generic types of Swift.Result:

// A value that represents either a success or a failure, including an
/// associated value in each case.
@frozen public enum Result<Success, Failure> where Failure : Error {

    /// A success, storing a `Success` value.
    case success(Success)

    /// A failure, storing a `Failure` value.
    case failure(Failure)


The generated .swiftinterface contains these declarations as expected, but when I try to compile the app it raises an "use of undeclared type" for both Success and Failure. How can I let the compiler know those are generic types?

This is definitely a bug -- any .swiftinterface that the compiler produces when BUILD_LIBRARY_FOR_DISTRIBUTION is enabled needs to be compilable. Is there any chance you can file it on bugs.swift.org and attach a small project that reproduces the issue?

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Thanks for coming back so quickly. I'll try to generate a minimal version with the current setup and file it.

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