diff --git a/tests/ui/lint/lint-ctypes-enum.rs b/tests/ui/lint/lint-ctypes-enum.rs
index c60290f8553a..8d60a8dd3171 100644
--- a/tests/ui/lint/lint-ctypes-enum.rs
+++ b/tests/ui/lint/lint-ctypes-enum.rs
@@ -55,38 +55,120 @@ union TransparentUnion<T: Copy> {
 
 struct Rust<T>(T);
 
+struct NoField;
+
+#[repr(transparent)]
+struct Field(());
+
+#[non_exhaustive]
+enum NonExhaustive {}
+
 extern "C" {
-   fn zf(x: Z);
-   fn uf(x: U); //~ ERROR `extern` block uses type `U`
-   fn bf(x: B); //~ ERROR `extern` block uses type `B`
-   fn tf(x: T); //~ ERROR `extern` block uses type `T`
-   fn repr_c(x: ReprC);
-   fn repr_u8(x: U8);
-   fn repr_isize(x: Isize);
-   fn option_ref(x: Option<&'static u8>);
-   fn option_fn(x: Option<extern "C" fn()>);
-   fn nonnull(x: Option<std::ptr::NonNull<u8>>);
-   fn unique(x: Option<std::ptr::Unique<u8>>);
-   fn nonzero_u8(x: Option<num::NonZero<u8>>);
-   fn nonzero_u16(x: Option<num::NonZero<u16>>);
-   fn nonzero_u32(x: Option<num::NonZero<u32>>);
-   fn nonzero_u64(x: Option<num::NonZero<u64>>);
-   fn nonzero_u128(x: Option<num::NonZero<u128>>);
-   //~^ ERROR `extern` block uses type `u128`
-   fn nonzero_usize(x: Option<num::NonZero<usize>>);
-   fn nonzero_i8(x: Option<num::NonZero<i8>>);
-   fn nonzero_i16(x: Option<num::NonZero<i16>>);
-   fn nonzero_i32(x: Option<num::NonZero<i32>>);
-   fn nonzero_i64(x: Option<num::NonZero<i64>>);
-   fn nonzero_i128(x: Option<num::NonZero<i128>>);
-   //~^ ERROR `extern` block uses type `i128`
-   fn nonzero_isize(x: Option<num::NonZero<isize>>);
-   fn transparent_struct(x: Option<TransparentStruct<num::NonZero<u8>>>);
-   fn transparent_enum(x: Option<TransparentEnum<num::NonZero<u8>>>);
-   fn transparent_union(x: Option<TransparentUnion<num::NonZero<u8>>>);
-   //~^ ERROR `extern` block uses type
-   fn repr_rust(x: Option<Rust<num::NonZero<u8>>>); //~ ERROR `extern` block uses type
-   fn no_result(x: Result<(), num::NonZero<i32>>); //~ ERROR `extern` block uses type
+    fn zf(x: Z);
+    fn uf(x: U); //~ ERROR `extern` block uses type `U`
+    fn bf(x: B); //~ ERROR `extern` block uses type `B`
+    fn tf(x: T); //~ ERROR `extern` block uses type `T`
+    fn repr_c(x: ReprC);
+    fn repr_u8(x: U8);
+    fn repr_isize(x: Isize);
+    fn option_ref(x: Option<&'static u8>);
+    fn option_fn(x: Option<extern "C" fn()>);
+    fn option_nonnull(x: Option<std::ptr::NonNull<u8>>);
+    fn option_unique(x: Option<std::ptr::Unique<u8>>);
+    fn option_nonzero_u8(x: Option<num::NonZero<u8>>);
+    fn option_nonzero_u16(x: Option<num::NonZero<u16>>);
+    fn option_nonzero_u32(x: Option<num::NonZero<u32>>);
+    fn option_nonzero_u64(x: Option<num::NonZero<u64>>);
+    fn option_nonzero_u128(x: Option<num::NonZero<u128>>);
+    //~^ ERROR `extern` block uses type `u128`
+    fn option_nonzero_usize(x: Option<num::NonZero<usize>>);
+    fn option_nonzero_i8(x: Option<num::NonZero<i8>>);
+    fn option_nonzero_i16(x: Option<num::NonZero<i16>>);
+    fn option_nonzero_i32(x: Option<num::NonZero<i32>>);
+    fn option_nonzero_i64(x: Option<num::NonZero<i64>>);
+    fn option_nonzero_i128(x: Option<num::NonZero<i128>>);
+    //~^ ERROR `extern` block uses type `i128`
+    fn option_nonzero_isize(x: Option<num::NonZero<isize>>);
+    fn option_transparent_struct(x: Option<TransparentStruct<num::NonZero<u8>>>);
+    fn option_transparent_enum(x: Option<TransparentEnum<num::NonZero<u8>>>);
+    fn option_transparent_union(x: Option<TransparentUnion<num::NonZero<u8>>>);
+    //~^ ERROR `extern` block uses type
+    fn option_repr_rust(x: Option<Rust<num::NonZero<u8>>>); //~ ERROR `extern` block uses type
+
+    fn result_ref_t(x: Result<&'static u8, ()>);
+    fn result_fn_t(x: Result<extern "C" fn(), ()>);
+    fn result_nonnull_t(x: Result<std::ptr::NonNull<u8>, ()>);
+    fn result_unique_t(x: Result<std::ptr::Unique<u8>, ()>);
+    fn result_nonzero_u8_t(x: Result<num::NonZero<u8>, ()>);
+    fn result_nonzero_u16_t(x: Result<num::NonZero<u16>, ()>);
+    fn result_nonzero_u32_t(x: Result<num::NonZero<u32>, ()>);
+    fn result_nonzero_u64_t(x: Result<num::NonZero<u64>, ()>);
+    fn result_nonzero_u128_t(x: Result<num::NonZero<u128>, ()>);
+    //~^ ERROR `extern` block uses type `u128`
+    fn result_nonzero_usize_t(x: Result<num::NonZero<usize>, ()>);
+    fn result_nonzero_i8_t(x: Result<num::NonZero<i8>, ()>);
+    fn result_nonzero_i16_t(x: Result<num::NonZero<i16>, ()>);
+    fn result_nonzero_i32_t(x: Result<num::NonZero<i32>, ()>);
+    fn result_nonzero_i64_t(x: Result<num::NonZero<i64>, ()>);
+    fn result_nonzero_i128_t(x: Result<num::NonZero<i128>, ()>);
+    //~^ ERROR `extern` block uses type `i128`
+    fn result_nonzero_isize_t(x: Result<num::NonZero<isize>, ()>);
+    fn result_transparent_struct_t(x: Result<TransparentStruct<num::NonZero<u8>>, ()>);
+    fn result_transparent_enum_t(x: Result<TransparentEnum<num::NonZero<u8>>, ()>);
+    fn result_transparent_union_t(x: Result<TransparentUnion<num::NonZero<u8>>, ()>);
+    //~^ ERROR `extern` block uses type
+    fn result_repr_rust_t(x: Result<Rust<num::NonZero<u8>>, ()>);
+    //~^ ERROR `extern` block uses type
+    fn result_phantom_t(x: Result<num::NonZero<u8>, std::marker::PhantomData<()>>);
+    fn result_1zst_exhaustive_no_variant_t(x: Result<num::NonZero<u8>, Z>);
+    fn result_1zst_exhaustive_single_variant_t(x: Result<num::NonZero<u8>, U>);
+    fn result_1zst_exhaustive_multiple_variant_t(x: Result<num::NonZero<u8>, B>);
+    //~^ ERROR `extern` block uses type
+    fn result_1zst_non_exhaustive_no_variant_t(x: Result<num::NonZero<u8>, NonExhaustive>);
+    //~^ ERROR `extern` block uses type
+    fn result_1zst_exhaustive_no_field_t(x: Result<num::NonZero<u8>, NoField>);
+    fn result_1zst_exhaustive_single_field_t(x: Result<num::NonZero<u8>, Field>);
+    //~^ ERROR `extern` block uses type
+    fn result_cascading_t(x: Result<Result<(), num::NonZero<u8>>, ()>);
+    //~^ ERROR `extern` block uses type
+
+    fn result_ref_e(x: Result<(), &'static u8>);
+    fn result_fn_e(x: Result<(), extern "C" fn()>);
+    fn result_nonnull_e(x: Result<(), std::ptr::NonNull<u8>>);
+    fn result_unique_e(x: Result<(), std::ptr::Unique<u8>>);
+    fn result_nonzero_u8_e(x: Result<(), num::NonZero<u8>>);
+    fn result_nonzero_u16_e(x: Result<(), num::NonZero<u16>>);
+    fn result_nonzero_u32_e(x: Result<(), num::NonZero<u32>>);
+    fn result_nonzero_u64_e(x: Result<(), num::NonZero<u64>>);
+    fn result_nonzero_u128_e(x: Result<(), num::NonZero<u128>>);
+    //~^ ERROR `extern` block uses type `u128`
+    fn result_nonzero_usize_e(x: Result<(), num::NonZero<usize>>);
+    fn result_nonzero_i8_e(x: Result<(), num::NonZero<i8>>);
+    fn result_nonzero_i16_e(x: Result<(), num::NonZero<i16>>);
+    fn result_nonzero_i32_e(x: Result<(), num::NonZero<i32>>);
+    fn result_nonzero_i64_e(x: Result<(), num::NonZero<i64>>);
+    fn result_nonzero_i128_e(x: Result<(), num::NonZero<i128>>);
+    //~^ ERROR `extern` block uses type `i128`
+    fn result_nonzero_isize_e(x: Result<(), num::NonZero<isize>>);
+    fn result_transparent_struct_e(x: Result<(), TransparentStruct<num::NonZero<u8>>>);
+    fn result_transparent_enum_e(x: Result<(), TransparentEnum<num::NonZero<u8>>>);
+    fn result_transparent_union_e(x: Result<(), TransparentUnion<num::NonZero<u8>>>);
+    //~^ ERROR `extern` block uses type
+    fn result_repr_rust_e(x: Result<(), Rust<num::NonZero<u8>>>);
+    //~^ ERROR `extern` block uses type
+    fn result_phantom_e(x: Result<num::NonZero<u8>, std::marker::PhantomData<()>>);
+    fn result_1zst_exhaustive_no_variant_e(x: Result<Z, num::NonZero<u8>>);
+    fn result_1zst_exhaustive_single_variant_e(x: Result<U, num::NonZero<u8>>);
+    fn result_1zst_exhaustive_multiple_variant_e(x: Result<B, num::NonZero<u8>>);
+    //~^ ERROR `extern` block uses type
+    fn result_1zst_non_exhaustive_no_variant_e(x: Result<NonExhaustive, num::NonZero<u8>>);
+    //~^ ERROR `extern` block uses type
+    fn result_1zst_exhaustive_no_field_e(x: Result<NoField, num::NonZero<u8>>);
+    fn result_1zst_exhaustive_single_field_e(x: Result<Field, num::NonZero<u8>>);
+    //~^ ERROR `extern` block uses type
+    fn result_cascading_e(x: Result<(), Result<(), num::NonZero<u8>>>);
+    //~^ ERROR `extern` block uses type
+
 }
 
 pub fn main() {}
diff --git a/tests/ui/lint/lint-ctypes-enum.stderr b/tests/ui/lint/lint-ctypes-enum.stderr
index 103fda8d4025..c982f040fb6f 100644
--- a/tests/ui/lint/lint-ctypes-enum.stderr
+++ b/tests/ui/lint/lint-ctypes-enum.stderr
@@ -1,8 +1,8 @@
 error: `extern` block uses type `U`, which is not FFI-safe
-  --> $DIR/lint-ctypes-enum.rs:60:13
+  --> $DIR/lint-ctypes-enum.rs:68:14
    |
-LL |    fn uf(x: U);
-   |             ^ not FFI-safe
+LL |     fn uf(x: U);
+   |              ^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
    = note: enum has no representation hint
@@ -18,10 +18,10 @@ LL | #![deny(improper_ctypes)]
    |         ^^^^^^^^^^^^^^^
 
 error: `extern` block uses type `B`, which is not FFI-safe
-  --> $DIR/lint-ctypes-enum.rs:61:13
+  --> $DIR/lint-ctypes-enum.rs:69:14
    |
-LL |    fn bf(x: B);
-   |             ^ not FFI-safe
+LL |     fn bf(x: B);
+   |              ^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
    = note: enum has no representation hint
@@ -32,10 +32,10 @@ LL | enum B {
    | ^^^^^^
 
 error: `extern` block uses type `T`, which is not FFI-safe
-  --> $DIR/lint-ctypes-enum.rs:62:13
+  --> $DIR/lint-ctypes-enum.rs:70:14
    |
-LL |    fn tf(x: T);
-   |             ^ not FFI-safe
+LL |     fn tf(x: T);
+   |              ^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
    = note: enum has no representation hint
@@ -46,47 +46,178 @@ LL | enum T {
    | ^^^^^^
 
 error: `extern` block uses type `u128`, which is not FFI-safe
-  --> $DIR/lint-ctypes-enum.rs:74:23
+  --> $DIR/lint-ctypes-enum.rs:82:31
    |
-LL |    fn nonzero_u128(x: Option<num::NonZero<u128>>);
-   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+LL |     fn option_nonzero_u128(x: Option<num::NonZero<u128>>);
+   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = note: 128-bit integers don't currently have a known stable ABI
 
 error: `extern` block uses type `i128`, which is not FFI-safe
-  --> $DIR/lint-ctypes-enum.rs:81:23
+  --> $DIR/lint-ctypes-enum.rs:89:31
    |
-LL |    fn nonzero_i128(x: Option<num::NonZero<i128>>);
-   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+LL |     fn option_nonzero_i128(x: Option<num::NonZero<i128>>);
+   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = note: 128-bit integers don't currently have a known stable ABI
 
 error: `extern` block uses type `Option<TransparentUnion<NonZero<u8>>>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-enum.rs:86:28
+  --> $DIR/lint-ctypes-enum.rs:94:36
    |
-LL |    fn transparent_union(x: Option<TransparentUnion<num::NonZero<u8>>>);
-   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+LL |     fn option_transparent_union(x: Option<TransparentUnion<num::NonZero<u8>>>);
+   |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
    = note: enum has no representation hint
 
 error: `extern` block uses type `Option<Rust<NonZero<u8>>>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-enum.rs:88:20
+  --> $DIR/lint-ctypes-enum.rs:96:28
    |
-LL |    fn repr_rust(x: Option<Rust<num::NonZero<u8>>>);
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+LL |     fn option_repr_rust(x: Option<Rust<num::NonZero<u8>>>);
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
    = note: enum has no representation hint
 
-error: `extern` block uses type `Result<(), NonZero<i32>>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-enum.rs:89:20
+error: `extern` block uses type `u128`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:106:33
    |
-LL |    fn no_result(x: Result<(), num::NonZero<i32>>);
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+LL |     fn result_nonzero_u128_t(x: Result<num::NonZero<u128>, ()>);
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
+
+error: `extern` block uses type `i128`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:113:33
+   |
+LL |     fn result_nonzero_i128_t(x: Result<num::NonZero<i128>, ()>);
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
+
+error: `extern` block uses type `Result<TransparentUnion<NonZero<u8>>, ()>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:118:38
+   |
+LL |     fn result_transparent_union_t(x: Result<TransparentUnion<num::NonZero<u8>>, ()>);
+   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
    = note: enum has no representation hint
 
-error: aborting due to 8 previous errors
+error: `extern` block uses type `Result<Rust<NonZero<u8>>, ()>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:120:30
+   |
+LL |     fn result_repr_rust_t(x: Result<Rust<num::NonZero<u8>>, ()>);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<NonZero<u8>, B>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:125:53
+   |
+LL |     fn result_1zst_exhaustive_multiple_variant_t(x: Result<num::NonZero<u8>, B>);
+   |                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<NonZero<u8>, NonExhaustive>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:127:51
+   |
+LL |     fn result_1zst_non_exhaustive_no_variant_t(x: Result<num::NonZero<u8>, NonExhaustive>);
+   |                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<NonZero<u8>, Field>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:130:49
+   |
+LL |     fn result_1zst_exhaustive_single_field_t(x: Result<num::NonZero<u8>, Field>);
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<Result<(), NonZero<u8>>, ()>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:132:30
+   |
+LL |     fn result_cascading_t(x: Result<Result<(), num::NonZero<u8>>, ()>);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `u128`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:143:33
+   |
+LL |     fn result_nonzero_u128_e(x: Result<(), num::NonZero<u128>>);
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
+
+error: `extern` block uses type `i128`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:150:33
+   |
+LL |     fn result_nonzero_i128_e(x: Result<(), num::NonZero<i128>>);
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = note: 128-bit integers don't currently have a known stable ABI
+
+error: `extern` block uses type `Result<(), TransparentUnion<NonZero<u8>>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:155:38
+   |
+LL |     fn result_transparent_union_e(x: Result<(), TransparentUnion<num::NonZero<u8>>>);
+   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<(), Rust<NonZero<u8>>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:157:30
+   |
+LL |     fn result_repr_rust_e(x: Result<(), Rust<num::NonZero<u8>>>);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<B, NonZero<u8>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:162:53
+   |
+LL |     fn result_1zst_exhaustive_multiple_variant_e(x: Result<B, num::NonZero<u8>>);
+   |                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<NonExhaustive, NonZero<u8>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:164:51
+   |
+LL |     fn result_1zst_non_exhaustive_no_variant_e(x: Result<NonExhaustive, num::NonZero<u8>>);
+   |                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<Field, NonZero<u8>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:167:49
+   |
+LL |     fn result_1zst_exhaustive_single_field_e(x: Result<Field, num::NonZero<u8>>);
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: `extern` block uses type `Result<(), Result<(), NonZero<u8>>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes-enum.rs:169:30
+   |
+LL |     fn result_cascading_e(x: Result<(), Result<(), num::NonZero<u8>>>);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+error: aborting due to 23 previous errors