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 | note: the lint level is defined here --> $DIR/union-repr-c.rs:2:9 | LL | #![deny(improper_ctypes)] | ^^^^^^^^^^^^^^^ = 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 { | ^^^^^^^ error: aborting due to previous error