error: `extern` block uses type `W`, which is not FFI-safe
  --> $DIR/union-repr-c.rs:15:22
   |
LL |     static FOREIGN2: W;
   |                      ^ not FFI-safe
   |
   = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this union
   = note: this union has unspecified layout
note: the type is defined here
  --> $DIR/union-repr-c.rs:9:1
   |
LL | union W {
   | ^^^^^^^
note: the lint level is defined here
  --> $DIR/union-repr-c.rs:2:9
   |
LL | #![deny(improper_ctypes)]
   |         ^^^^^^^^^^^^^^^

error: aborting due to 1 previous error