1 files changed, 36 insertions, 0 deletions
diff --git a/tests/ui/packed/packed-struct-optimized-enum.rs b/tests/ui/packed/packed-struct-optimized-enum.rs
new file mode 100644
index 00000000000..5e1a1f518c5
--- /dev/null
+++ b/tests/ui/packed/packed-struct-optimized-enum.rs
@@ -0,0 +1,36 @@
+// run-pass
+#[repr(packed)]
+struct Packed<T: Copy>(#[allow(unused_tuple_struct_fields)] T);
+
+impl<T: Copy> Copy for Packed<T> {}
+impl<T: Copy> Clone for Packed<T> {
+    fn clone(&self) -> Self { *self }
+}
+
+fn sanity_check_size<T: Copy>(one: T) {
+    let two = [one, one];
+    let stride = (&two[1] as *const _ as usize) - (&two[0] as *const _ as usize);
+    let (size, align) = (std::mem::size_of::<T>(), std::mem::align_of::<T>());
+    assert_eq!(stride, size);
+    assert_eq!(size % align, 0);
+}
+
+fn main() {
+    // This can fail if rustc and LLVM disagree on the size of a type.
+    // In this case, `Option<Packed<(&(), u32)>>` was erroneously not
+    // marked as packed despite needing alignment `1` and containing
+    // its `&()` discriminant, which has alignment larger than `1`.
+    sanity_check_size((Some(Packed((&(), 0))), true));
+
+    // In #46769, `Option<(Packed<&()>, bool)>` was found to have
+    // pointer alignment, without actually being aligned in size.
+    // e.g., on 64-bit platforms, it had alignment `8` but size `9`.
+    type PackedRefAndBool<'a> = (Packed<&'a ()>, bool);
+    sanity_check_size::<Option<PackedRefAndBool>>(Some((Packed(&()), true)));
+
+    // Make sure we don't pay for the enum optimization in size,
+    // e.g., we shouldn't need extra padding after the packed data.
+    assert_eq!(std::mem::align_of::<Option<PackedRefAndBool>>(), 1);
+    assert_eq!(std::mem::size_of::<Option<PackedRefAndBool>>(),
+               std::mem::size_of::<PackedRefAndBool>());
+}