Add more ABI test cases.

src/tools/miri/tests/pass/function_calls/abi_compat.rs

@@ -83,12 +83,24 @@ fn main() {
     test_abi_compat(main as fn(), id::<i32> as fn(i32) -> i32);
     // - 1-ZST
     test_abi_compat((), [0u8; 0]);
-    // - Guaranteed null-pointer-optimizations (RFC 3391).
+    // - Guaranteed Option<X> null-pointer-optimizations (RFC 3391).
     test_abi_compat(&0u32 as *const u32, Some(&0u32));
     test_abi_compat(main as fn(), Some(main as fn()));
     test_abi_compat(0u32, Some(num::NonZero::new(1u32).unwrap()));
     test_abi_compat(&0u32 as *const u32, Some(Wrapper(&0u32)));
-    test_abi_compat(0u32, Some(Wrapper(num::NonZero::new(1u32).unwrap())));
+    test_abi_compat(0u32, Some(Wrapper(num::NonZeroU32::new(1u32).unwrap())));
+    // - Guaranteed Result<X, ZST1> does the same as Option<X> (RFC 3391)
+    test_abi_compat(&0u32 as *const u32, Result::<_, ()>::Ok(&0u32));
+    test_abi_compat(main as fn(), Result::<_, ()>::Ok(main as fn()));
+    test_abi_compat(0u32, Result::<_, ()>::Ok(num::NonZeroU32::new(1).unwrap()));
+    test_abi_compat(&0u32 as *const u32, Result::<_, ()>::Ok(Wrapper(&0u32)));
+    test_abi_compat(0u32, Result::<_, ()>::Ok(Wrapper(num::NonZeroU32::new(1).unwrap())));
+    // - Guaranteed Result<ZST1, X> also does the same as Option<X> (RFC 3391)
+    test_abi_compat(&0u32 as *const u32, Result::<(), _>::Err(&0u32));
+    test_abi_compat(main as fn(), Result::<(), _>::Err(main as fn()));
+    test_abi_compat(0u32, Result::<(), _>::Err(num::NonZeroU32::new(1).unwrap()));
+    test_abi_compat(&0u32 as *const u32, Result::<(), _>::Err(Wrapper(&0u32)));
+    test_abi_compat(0u32, Result::<(), _>::Err(Wrapper(num::NonZeroU32::new(1).unwrap())));
 
     // These must work for *any* type, since we guarantee that `repr(transparent)` is ABI-compatible
     // with the wrapped field.