error: `extern` block uses type `U` which is not FFI-safe: enum has no representation hint
  --> $DIR/lint-ctypes-enum.rs:39:13
   |
LL |    fn uf(x: U);
   |             ^
   |
note: lint level defined here
  --> $DIR/lint-ctypes-enum.rs:3:9
   |
LL | #![deny(improper_ctypes)]
   |         ^^^^^^^^^^^^^^^
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
note: type defined here
  --> $DIR/lint-ctypes-enum.rs:9:1
   |
LL | enum U { A }
   | ^^^^^^^^^^^^

error: `extern` block uses type `B` which is not FFI-safe: enum has no representation hint
  --> $DIR/lint-ctypes-enum.rs:40:13
   |
LL |    fn bf(x: B);
   |             ^
   |
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
note: type defined here
  --> $DIR/lint-ctypes-enum.rs:10:1
   |
LL | enum B { C, D }
   | ^^^^^^^^^^^^^^^

error: `extern` block uses type `T` which is not FFI-safe: enum has no representation hint
  --> $DIR/lint-ctypes-enum.rs:41:13
   |
LL |    fn tf(x: T);
   |             ^
   |
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
note: type defined here
  --> $DIR/lint-ctypes-enum.rs:11:1
   |
LL | enum T { E, F, G }
   | ^^^^^^^^^^^^^^^^^^

error: `extern` block uses type `std::option::Option<std::ptr::Unique<u8>>` which is not FFI-safe: enum has no representation hint
  --> $DIR/lint-ctypes-enum.rs:48:17
   |
LL |    fn unique(x: Option<std::ptr::Unique<u8>>);
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum

error: `extern` block uses type `u128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
  --> $DIR/lint-ctypes-enum.rs:53:23
   |
LL |    fn nonzero_u128(x: Option<num::NonZeroU128>);
   |                       ^^^^^^^^^^^^^^^^^^^^^^^^

error: `extern` block uses type `i128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
  --> $DIR/lint-ctypes-enum.rs:60:23
   |
LL |    fn nonzero_i128(x: Option<num::NonZeroI128>);
   |                       ^^^^^^^^^^^^^^^^^^^^^^^^

error: `extern` block uses type `std::option::Option<TransparentUnion<std::num::NonZeroU8>>` which is not FFI-safe: enum has no representation hint
  --> $DIR/lint-ctypes-enum.rs:65:28
   |
LL |    fn transparent_union(x: Option<TransparentUnion<num::NonZeroU8>>);
   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum

error: `extern` block uses type `std::option::Option<Rust<std::num::NonZeroU8>>` which is not FFI-safe: enum has no representation hint
  --> $DIR/lint-ctypes-enum.rs:67:20
   |
LL |    fn repr_rust(x: Option<Rust<num::NonZeroU8>>);
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum

error: `extern` block uses type `std::result::Result<(), std::num::NonZeroI32>` which is not FFI-safe: enum has no representation hint
  --> $DIR/lint-ctypes-enum.rs:68:20
   |
LL |    fn no_result(x: Result<(), num::NonZeroI32>);
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum

error: aborting due to 9 previous errors