Rollup merge of rust-lang#132002 - RalfJung:abi-compat-option-like, r…

…=compiler-errors

abi/compatibility: also test Option-like types

Adds tests for the decision [here](rust-lang#130628 (comment)).

Cc `@workingjubilee`

tests/ui/abi/compatibility.rs

@@ -211,6 +211,15 @@ impl Clone for Zst {
     }
 }
 
+enum Either<T, U> {
+    Left(T),
+    Right(U),
+}
+enum Either2<T, U> {
+    Left(T),
+    Right(U, ()),
+}
+
 #[repr(C)]
 enum ReprCEnum<T> {
     Variant1,
@@ -328,7 +337,8 @@ mod unsized_ {
     test_transparent_unsized!(dyn_trait, dyn Any);
 }
 
-// RFC 3391 <https://rust-lang.github.io/rfcs/3391-result_ffi_guarantees.html>.
+// RFC 3391 <https://rust-lang.github.io/rfcs/3391-result_ffi_guarantees.html>, including the
+// extension ratified at <https://github.com/rust-lang/rust/pull/130628#issuecomment-2402761599>.
 macro_rules! test_nonnull {
     ($name:ident, $t:ty) => {
         mod $name {
@@ -340,6 +350,12 @@ macro_rules! test_nonnull {
             test_abi_compatible!(result_ok_zst, Result<Zst, $t>, $t);
             test_abi_compatible!(result_err_arr, Result<$t, [i8; 0]>, $t);
             test_abi_compatible!(result_ok_arr, Result<[i8; 0], $t>, $t);
+            test_abi_compatible!(result_err_void, Result<$t, Void>, $t);
+            test_abi_compatible!(result_ok_void, Result<Void, $t>, $t);
+            test_abi_compatible!(either_err_zst, Either<$t, Zst>, $t);
+            test_abi_compatible!(either_ok_zst, Either<Zst, $t>, $t);
+            test_abi_compatible!(either2_err_zst, Either2<$t, Zst>, $t);
+            test_abi_compatible!(either2_err_arr, Either2<$t, [i8; 0]>, $t);
         }
     }
 }