1 files changed, 31 insertions, 0 deletions
diff --git a/src/test/ui/transmutability/structs/should_order_fields_correctly.rs b/src/test/ui/transmutability/structs/should_order_fields_correctly.rs
new file mode 100644
index 000000000..db49b914f
--- /dev/null
+++ b/src/test/ui/transmutability/structs/should_order_fields_correctly.rs
@@ -0,0 +1,31 @@
+// check-pass
+//! The fields of a struct should be laid out in lexical order.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+    use std::mem::BikeshedIntrinsicFrom;
+    pub struct Context;
+
+    pub fn is_transmutable<Src, Dst>()
+    where
+        Dst: BikeshedIntrinsicFrom<Src, Context, true, true, true, true>
+    {}
+}
+
+#[repr(u8)] enum V0 { V = 0 }
+#[repr(u8)] enum V1 { V = 1 }
+#[repr(u8)] enum V2 { V = 2 }
+
+#[repr(C)] struct S01(V0, V1);
+#[repr(C)] struct S012(V0, V1, V2);
+
+fn should_order_tag_and_fields_correctly() {
+    // An implementation that (incorrectly) arranges S01 as [0x01, 0x00] will,
+    // in principle, reject this transmutation.
+    assert::is_transmutable::<S01, V0>();
+    // Again, but with one more field.
+    assert::is_transmutable::<S012, S01>();
+}