1 error: `extern` block uses type `Foo`, which is not FFI-safe
2 --> $DIR/issue-16250.rs:6:20
4 LL | pub fn foo(x: (Foo));
7 = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
8 = note: this struct has unspecified layout
9 note: the type is defined here
10 --> $DIR/issue-16250.rs:3:1
14 note: the lint level is defined here
15 --> $DIR/issue-16250.rs:1:9
17 LL | #![deny(warnings)]
19 = note: `#[deny(improper_ctypes)]` implied by `#[deny(warnings)]`
21 error: aborting due to previous error