// Swift 6.4 (swiftlang-6.4.0.34.1): an address-only ~Escapable value escapes its borrow through an Optional.
// swiftc -enable-experimental-feature Lifetimes repro.swift -o repro && ./repro
// swiftc -enable-experimental-feature Lifetimes -DNEGATIVE repro.swift     (the shapes the compiler refuses)

struct View: ~Escapable {
    let span: Span<UInt8>
    let tag: Any = ()   // address-only, as a non-frozen public type from a library-evolution build is in its clients; drop this line and every shape below is refused
    @_lifetime(copy span) init(_ span: Span<UInt8>) { self.span = span }
    var first: UInt8 { span[0] }
}

struct Owner {
    var bytes: [UInt8] = [1, 2, 3, 4]
    var view: View { @_lifetime(borrow self) get { View(bytes.span) } }
    func withView(_ body: (View) -> Void) { body(view) }
    func withOptionalView(_ body: (View?) -> Void) { body(view) }
}

func escape() {
    var owner = Owner()
    var kept: View? = nil
    owner.withView { view in kept = view }                          // compiles: the view outlives the lend
    print("kept view after the lend:", kept!.first)                 // 1
    owner.bytes[0] = 9                                              // the owner is mutated while the view is held
    print("kept view after the owner changed:", kept!.first)        // 9: the view still aliases the owner
    owner.withOptionalView { view in if let view { kept = view } }  // compiles as well
    do { let local = Owner(); kept = local.view }                   // compiles as well, no closure involved
    print("kept view of a dead owner:", kept!.first)                // reads freed memory
}
escape()

#if NEGATIVE
func refused(_ owner: Owner) {
    var direct: View = owner.view
    owner.withView { view in direct = view }        // error: lifetime-dependent variable 'direct' escapes its scope
    var kept: View? = nil
    owner.withOptionalView { view in kept = view }  // error: lifetime-dependent variable 'kept' escapes its scope
    print(direct.first, kept!.first)
}
#endif