Add tests for >1-aligned ZSTs + extern type in a transparent struct

Author: mjbshaw

src/test/ui/repr/repr-transparent.rs

@@ -13,7 +13,7 @@
 // - repr-transparent-other-reprs.rs
 // - repr-transparent-other-items.rs
 
-#![feature(repr_align)]
+#![feature(extern_types, repr_align)]
 
 use std::marker::PhantomData;
 
@@ -49,4 +49,14 @@ struct ZstAlign32<T>(PhantomData<T>);
 #[repr(transparent)]
 struct GenericAlign<T>(ZstAlign32<T>, u32); //~ ERROR alignment larger than 1
 
+extern "C" {
+    type ExternType;
+}
+
+#[repr(transparent)]
+struct NontrivialAlignZstExtern([u16; 0], ExternType); //~ ERROR alignment larger than 1
+
+#[repr(transparent)]
+struct GenericAlignExtern<T>(ZstAlign32<T>, ExternType); //~ ERROR alignment larger than 1
+
 fn main() {}

src/test/ui/repr/repr-transparent.stderr

@@ -66,7 +66,19 @@ error[E0691]: zero-sized field in transparent struct has alignment larger than 1
 LL | struct GenericAlign<T>(ZstAlign32<T>, u32); //~ ERROR alignment larger than 1
    |                        ^^^^^^^^^^^^^
 
-error: aborting due to 8 previous errors
+error[E0691]: zero-sized field in transparent struct has alignment larger than 1
+  --> $DIR/repr-transparent.rs:57:33
+   |
+LL | struct NontrivialAlignZstExtern([u16; 0], ExternType); //~ ERROR alignment larger than 1
+   |                                 ^^^^^^^^
+
+error[E0691]: zero-sized field in transparent struct has alignment larger than 1
+  --> $DIR/repr-transparent.rs:60:30
+   |
+LL | struct GenericAlignExtern<T>(ZstAlign32<T>, ExternType); //~ ERROR alignment larger than 1
+   |                              ^^^^^^^^^^^^^
+
+error: aborting due to 10 previous errors
 
 Some errors occurred: E0690, E0691.
 For more information about an error, try `rustc --explain E0690`.