error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
  --> $DIR/issue-14309.rs:40:15
   |
LL |     fn foo(x: A); //~ ERROR type `A` which is not FFI-safe
   |               ^
   |
note: lint level defined here
  --> $DIR/issue-14309.rs:11:9
   |
LL | #![deny(improper_ctypes)]
   |         ^^^^^^^^^^^^^^^
   = help: consider adding a #[repr(C)] or #[repr(transparent)] attribute to this struct
note: type defined here
  --> $DIR/issue-14309.rs:14:1
   |
LL | / struct A {
LL | |     x: i32
LL | | }
   | |_^

error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
  --> $DIR/issue-14309.rs:41:15
   |
LL |     fn bar(x: B); //~ ERROR type `A`
   |               ^
   |
   = help: consider adding a #[repr(C)] or #[repr(transparent)] attribute to this struct
note: type defined here
  --> $DIR/issue-14309.rs:14:1
   |
LL | / struct A {
LL | |     x: i32
LL | | }
   | |_^

error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
  --> $DIR/issue-14309.rs:43:15
   |
LL |     fn qux(x: A2); //~ ERROR type `A`
   |               ^^
   |
   = help: consider adding a #[repr(C)] or #[repr(transparent)] attribute to this struct
note: type defined here
  --> $DIR/issue-14309.rs:14:1
   |
LL | / struct A {
LL | |     x: i32
LL | | }
   | |_^

error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
  --> $DIR/issue-14309.rs:44:16
   |
LL |     fn quux(x: B2); //~ ERROR type `A`
   |                ^^
   |
   = help: consider adding a #[repr(C)] or #[repr(transparent)] attribute to this struct
note: type defined here
  --> $DIR/issue-14309.rs:14:1
   |
LL | / struct A {
LL | |     x: i32
LL | | }
   | |_^

error: `extern` block uses type `A` which is not FFI-safe: this struct has unspecified layout
  --> $DIR/issue-14309.rs:46:16
   |
LL |     fn fred(x: D); //~ ERROR type `A`
   |                ^
   |
   = help: consider adding a #[repr(C)] or #[repr(transparent)] attribute to this struct
note: type defined here
  --> $DIR/issue-14309.rs:14:1
   |
LL | / struct A {
LL | |     x: i32
LL | | }
   | |_^

error: aborting due to 5 previous errors