Fix exception feature (broken since #21)

Author: madsmtm

objc2/src/exception.rs

@@ -1,8 +1,8 @@
 use core::ptr::NonNull;
 
-use crate::rc::Id;
+use crate::rc::{Id, Shared};
 use crate::runtime::Object;
-use objc2_exception::{r#try, Exception};
+use objc2_exception::r#try;
 
 // Comment copied from `objc2_exception`
 
@@ -21,6 +21,8 @@ use objc2_exception::{r#try, Exception};
 /// undefined behaviour until `C-unwind` is stabilized, see [RFC-2945].
 ///
 /// [RFC-2945]: https://rust-lang.github.io/rfcs/2945-c-unwind-abi.html
-pub unsafe fn catch_exception<R>(closure: impl FnOnce() -> R) -> Result<R, Id<Exception>> {
-    r#try(closure).map_err(|e| Id::new(NonNull::new(e).unwrap()))
+pub unsafe fn catch_exception<R>(
+    closure: impl FnOnce() -> R,
+) -> Result<R, Option<Id<Object, Shared>>> {
+    r#try(closure).map_err(|e| NonNull::new(e).map(|e| Id::new(e.cast())))
 }

objc2/src/message/mod.rs

@@ -14,10 +14,10 @@ macro_rules! objc_try {
     ($b:block) => {
         $crate::exception::catch_exception(|| $b).map_err(|exception| {
             use alloc::borrow::ToOwned;
-            if exception.is_null() {
-                MessageError("Uncaught exception nil".to_owned())
+            if let Some(exception) = exception {
+                MessageError(alloc::format!("Uncaught exception {:?}", exception))
             } else {
-                MessageError(alloc::format!("Uncaught exception {:?}", &**exception))
+                MessageError("Uncaught exception nil".to_owned())
             }
         })
     };