Account for unknown size with repr(C)

Author: daxpedda

src/item.rs

@@ -98,12 +98,13 @@ impl Item<'_> {
 /// Type of discriminant used.
 #[cfg_attr(test, derive(Debug))]
 pub enum Discriminant {
+	/// The enum uses the default representation but has a non-unit variant or
+	/// an enum with a C representation without an integer representation.
+	Unknown,
 	/// The enum has only a single variant.
 	Single,
 	/// The enum uses the default representation and has only unit variants.
 	UnitDefault,
-	/// The enum uses the default representation but has a non-unit variant.
-	Default,
 	/// The enum uses a non-default representation and has only unit variants.
 	UnitRepr(Representation),
 	/// The enum uses a non-default representation and has a non-unit variant.
@@ -118,6 +119,7 @@ impl Discriminant {
 		}
 
 		let mut has_repr = None;
+		let mut is_c = false;
 
 		for attr in attrs {
 			if attr.path().is_ident("repr") {
@@ -126,7 +128,9 @@ impl Discriminant {
 						list.parse_args_with(Punctuated::<Ident, Token![,]>::parse_terminated)?;
 
 					for ident in list {
-						if let Some(repr) = Representation::parse(&ident) {
+						if ident == "C" {
+							is_c = true;
+						} else if let Some(repr) = Representation::parse(&ident) {
 							has_repr = Some(repr);
 							break;
 						}
@@ -145,10 +149,10 @@ impl Discriminant {
 			} else {
 				Self::Repr(repr)
 			}
-		} else if is_unit {
+		} else if is_unit && !is_c {
 			Self::UnitDefault
 		} else {
-			Self::Default
+			Self::Unknown
 		})
 	}
 }

src/trait_/common_ord.rs

@@ -128,7 +128,7 @@ pub fn build_ord_signature(item: &Item, trait_: &DeriveTrait, body: &TokenStream
 								__other as isize,
 							)
 						},
-						Discriminant::Default => {
+						Discriminant::Unknown => {
 							build_recursive_order(trait_, variants, &incomparable)
 						}
 						Discriminant::UnitRepr(repr) => quote! {

tests/discriminant.rs

@@ -128,66 +128,6 @@ fn repr_with_discriminants_values() {
 	assert_eq!(5, unsafe { *<*const _>::from(&Test::C).cast::<u8>() });
 }
 
-#[test]
-fn repr_c() {
-	#[repr(C)]
-	enum Test {
-		A,
-		B,
-		C,
-	}
-
-	#[cfg(feature = "nightly")]
-	{
-		assert_eq!(0_isize, discriminant_value(&Test::A));
-		assert_eq!(1_isize, discriminant_value(&Test::B));
-		assert_eq!(2_isize, discriminant_value(&Test::C));
-	}
-	assert_eq!(0, Test::A as isize);
-	assert_eq!(1, Test::B as isize);
-	assert_eq!(2, Test::C as isize);
-}
-
-#[test]
-fn repr_c_with_discriminants() {
-	#[repr(C)]
-	enum Test {
-		A = 3,
-		B,
-		C,
-	}
-
-	#[cfg(feature = "nightly")]
-	{
-		assert_eq!(3_isize, discriminant_value(&Test::A));
-		assert_eq!(4_isize, discriminant_value(&Test::B));
-		assert_eq!(5_isize, discriminant_value(&Test::C));
-	}
-	assert_eq!(3, Test::A as isize);
-	assert_eq!(4, Test::B as isize);
-	assert_eq!(5, Test::C as isize);
-}
-
-#[test]
-fn repr_c_with_values() {
-	#[repr(C)]
-	enum Test {
-		A(u8),
-		B,
-		C,
-	}
-
-	#[cfg(feature = "nightly")]
-	{
-		assert_eq!(0_isize, discriminant_value(&Test::A(0)));
-		assert_eq!(1_isize, discriminant_value(&Test::B));
-		assert_eq!(2_isize, discriminant_value(&Test::C));
-	}
-	assert_eq!(0, unsafe { *<*const _>::from(&Test::A(0)).cast::<isize>() });
-	assert_eq!(1, unsafe { *<*const _>::from(&Test::B).cast::<isize>() });
-	assert_eq!(2, unsafe { *<*const _>::from(&Test::C).cast::<isize>() });
-}
-
 #[test]
 fn repr_with_repr_c_with_values() {
 	#[repr(C, u8)]