error: `extern` block uses type `U` which is not FFI-safe: enum has no representation hint
  --> $DIR/lint-ctypes-enum.rs:30:13
   |
LL |    fn uf(x: U); //~ ERROR enum has no representation hint
   |             ^
   |
note: lint level defined here
  --> $DIR/lint-ctypes-enum.rs:11:9
   |
LL | #![deny(improper_ctypes)]
   |         ^^^^^^^^^^^^^^^
   = help: consider adding a #[repr(...)] attribute to this enum
note: type defined here
  --> $DIR/lint-ctypes-enum.rs:15:1
   |
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:31:13
   |
LL |    fn bf(x: B); //~ ERROR enum has no representation hint
   |             ^
   |
   = help: consider adding a #[repr(...)] attribute to this enum
note: type defined here
  --> $DIR/lint-ctypes-enum.rs:16:1
   |
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:32:13
   |
LL |    fn tf(x: T); //~ ERROR enum has no representation hint
   |             ^
   |
   = help: consider adding a #[repr(...)] attribute to this enum
note: type defined here
  --> $DIR/lint-ctypes-enum.rs:17:1
   |
LL | enum T { E, F, G }
   | ^^^^^^^^^^^^^^^^^^

error: aborting due to 3 previous errors