❯ swift repl Welcome to Apple Swift version 6.2 (swiftlang-6.2.0.19.9 clang-1700.3.19.1). Type :help for assistance. 1> struct S { 2. var hoge: Int! 3. } 4. 5. let aa: KeyPath<S, Int> = \S.hoge 6. let ii: KeyPath<S, Int!> = \S.hoge 7. let uu: KeyPath<S, Int?> = \S.hoge 8. print(aa, ii, uu) \S.hoge! \S.hoge \S.hoge aa: WritableKeyPath<S, Int> = { Swift.KeyPath<__lldb_expr_1.S, Swift.Int> = { Swift.PartialKeyPath<__lldb_expr_1.S> = { Swift.AnyKeyPath = { _kvcKeyPathStringPtr = nil } } } } ii: WritableKeyPath<S, Int?> = { Swift.KeyPath<__lldb_expr_1.S, Swift.Optional<Swift.Int>> = { Swift.PartialKeyPath<__lldb_expr_1.S> = { Swift.AnyKeyPath = { _kvcKeyPathStringPtr = 0xffffffffffffffff } } } } uu: WritableKeyPath<S, Int?> = { Swift.KeyPath<__lldb_expr_1.S, Swift.Optional<Swift.Int>> = { Swift.PartialKeyPath<__lldb_expr_1.S> = { Swift.AnyKeyPath = { _kvcKeyPathStringPtr = 0xffffffffffffffff } } } } 9>