1 files changed, 45 insertions, 0 deletions
diff --git a/src/test/ui/derives/deriving-with-repr-packed.rs b/src/test/ui/derives/deriving-with-repr-packed.rs
new file mode 100644
index 000000000..3884e3977
--- /dev/null
+++ b/src/test/ui/derives/deriving-with-repr-packed.rs
@@ -0,0 +1,45 @@
+#![deny(unaligned_references)]
+
+// Check that deriving certain builtin traits on certain packed structs cause
+// errors. This happens when the derived trait would need to use a potentially
+// misaligned reference. But there are two cases that are allowed:
+// - If all the fields within the struct meet the required alignment: 1 for
+//   `repr(packed)`, or `N` for `repr(packed(N))`.
+// - If `Default` is the only trait derived, because it doesn't involve any
+//   references.
+
+#[derive(Copy, Clone, Default, PartialEq, Eq)]
+//~^ ERROR `Clone` can't be derived on this `#[repr(packed)]` struct with type or const parameters
+//~| hard error
+//~^^^ ERROR `PartialEq` can't be derived on this `#[repr(packed)]` struct with type or const parameters
+//~| hard error
+#[repr(packed)]
+pub struct Foo<T>(T, T, T);
+
+#[derive(Default, Hash)]
+//~^ ERROR `Hash` can't be derived on this `#[repr(packed)]` struct that does not derive `Copy`
+//~| hard error
+#[repr(packed)]
+pub struct Bar(u32, u32, u32);
+
+// This one is fine because the field alignment is 1.
+#[derive(Default, Hash)]
+#[repr(packed)]
+pub struct Bar2(u8, i8, bool);
+
+// This one is fine because the field alignment is 2, matching `packed(2)`.
+#[derive(Default, Hash)]
+#[repr(packed(2))]
+pub struct Bar3(u16, i16, bool);
+
+// This one is fine because it's not packed.
+#[derive(Debug, Default)]
+struct Y(usize);
+
+#[derive(Debug, Default)]
+//~^ ERROR `Debug` can't be derived on this `#[repr(packed)]` struct that does not derive `Copy`
+//~| hard error
+#[repr(packed)]
+struct X(Y);
+
+fn main() {}