1 files changed, 49 insertions, 0 deletions
diff --git a/third_party/rust/objc/src/message/verify.rs b/third_party/rust/objc/src/message/verify.rs
new file mode 100644
index 0000000000..61bd4ebb39
--- /dev/null
+++ b/third_party/rust/objc/src/message/verify.rs
@@ -0,0 +1,49 @@
+use runtime::{Class, Object, Sel};
+use {Encode, EncodeArguments};
+use super::MessageError;
+
+pub fn verify_message_signature<A, R>(cls: &Class, sel: Sel)
+        -> Result<(), MessageError>
+        where A: EncodeArguments, R: Encode {
+    let method = match cls.instance_method(sel) {
+        Some(method) => method,
+        None => return Err(MessageError(
+            format!("Method {:?} not found on class {:?}",
+                sel, cls)
+        )),
+    };
+
+    let ret = R::encode();
+    let expected_ret = method.return_type();
+    if ret != expected_ret {
+        return Err(MessageError(
+            format!("Return type code {:?} does not match expected {:?} for method {:?}",
+                ret, expected_ret, method.name())
+        ));
+    }
+
+    let self_and_cmd = [<*mut Object>::encode(), Sel::encode()];
+    let args = A::encodings();
+    let args = args.as_ref();
+
+    let count = self_and_cmd.len() + args.len();
+    let expected_count = method.arguments_count();
+    if count != expected_count {
+        return Err(MessageError(
+            format!("Method {:?} accepts {} arguments, but {} were given",
+                method.name(), expected_count, count)
+        ));
+    }
+
+    for (i, arg) in self_and_cmd.iter().chain(args).enumerate() {
+        let expected = method.argument_type(i).unwrap();
+        if *arg != expected {
+            return Err(MessageError(
+                format!("Method {:?} expected argument at index {} with type code {:?} but was given {:?}",
+                    method.name(), i, expected, arg)
+            ));
+        }
+    }
+
+    Ok(())
+}