@available(macOS 50, *)
public func conditionallyAvailableFunction() {}

@available(macOS, unavailable)
public func unavailableFunction() {}

@available(macOS 50, *)
public func conditionallyAvailableOpaqueReturnFunction() -> some AlwaysAvailableProtocol {
  return AlwaysAvailableStruct()
}

@available(macOS 50, *)
public var conditionallyAvailableGlobal: Int {
  get {return 0}
  set {}
}

@available(macOS, unavailable)
public var unavailableGlobal: Int {
  get {return 0}
  set {}
}

@available(macOS 50, *)
public struct ConditionallyAvailableStruct {
  public func conditionallyAvailableMethod() {}
}

extension ConditionallyAvailableStruct {
  public struct NestedStruct {}
}

@available(macOS, unavailable)
public struct UnavailableStruct {
  public func unavailableMethod() {}
}

public protocol AlwaysAvailableProtocol {}

public struct AlwaysAvailableStruct {}

@available(macOS 50, *)
extension AlwaysAvailableStruct {
  public func methodInConditionallyAvailableExtension() {}

  public func opaqueReturnMethodInConditionallyAvailableExtension() -> some AlwaysAvailableProtocol {
    return AlwaysAvailableStruct()
  }

  public var varInConditionallyAvailableExtension: Int {
    get {return 0}
    set {}
  }
}

extension AlwaysAvailableStruct {
  @available(macOS 50, *)
  public func conditionallyAvailableMethodInExtension() {}

  @available(macOS 50, *)
  public func conditionallyAvailableOpaqueReturnMethodInExtension() -> some AlwaysAvailableProtocol {
    return AlwaysAvailableStruct()
  }

  @available(macOS 50, *)
  public var conditionallyAvailableVarInExtension: Int {
    get {return 0}
    set {}
  }
}

@available(macOS 10.9, *)
extension AlwaysAvailableStruct {
  @available(macOS 50, *)
  public func conditionallyAvailableMethodInExplicitlyAvailableExtension() {}

  @available(macOS 50, *)
  public func conditionallyAvailableOpaqueReturnMethodInExplicitlyAvailableExtension() -> some AlwaysAvailableProtocol {
    return AlwaysAvailableStruct()
  }

  @available(macOS 50, *)
  public var conditionallyAvailableVarInExplicitlyAvailablextension: Int {
    get {return 0}
    set {}
  }
}

@available(macOS 50, *)
extension AlwaysAvailableStruct : AlwaysAvailableProtocol {}

@available(macOS, unavailable)
public protocol UnavailableProtocol {}

@available(macOS, unavailable)
extension AlwaysAvailableStruct : UnavailableProtocol {}

public enum AlwaysAvailableEnum {
  case alwaysAvailableCase

  @available(macOS 50, *)
  case conditionallyAvailableCase
}