Mark FuncDefn as non_exhaustive

Author: acl-cqc

hugr-core/src/ops/module.rs

@@ -52,6 +52,7 @@ impl OpTrait for Module {
 /// Children nodes are the body of the definition.
 #[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 #[cfg_attr(test, derive(Arbitrary))]
+#[non_exhaustive]
 pub struct FuncDefn {
     /// Name of function
     #[cfg_attr(test, proptest(strategy = "any_nonempty_string()"))]