Ensure that all values in FnAttribute::NonNull are positive

Author: GuillaumeGomez

src/function.rs

@@ -80,7 +80,13 @@ impl<'a> FnAttribute<'a> {
             | FnAttribute::Pure
             | FnAttribute::Const
             | FnAttribute::Weak => AttributeValue::None,
-            FnAttribute::NonNull(ref value) => AttributeValue::IntArray(value),
+            FnAttribute::NonNull(ref value) => {
+                debug_assert!(
+                    value.iter().all(|attr| *attr > 0),
+                    "all values must be > 0 for non-null attribute",
+                );
+                AttributeValue::IntArray(value)
+            }
         }
     }