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 note: the lint level is defined here
8 --> $DIR/issue-16250.rs:1:9
10 LL | #![deny(warnings)]
12 = note: `#[deny(improper_ctypes)]` implied by `#[deny(warnings)]`
13 = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
14 = note: this struct has unspecified layout
15 note: the type is defined here
16 --> $DIR/issue-16250.rs:3:1
21 error: aborting due to previous error