Implement check for memory corruption

nac3core/src/typecheck/function_check.rs

@@ -249,6 +249,8 @@ impl Inferencer<'_> {
             true
         } else {
             match &*self.unifier.get_ty_immutable(ret_ty) {
+                // For an object type, only allow a select few primitive types.
+                // (Note: you may wish to also allow strings if that’s acceptable.)
                 TypeEnum::TObj { .. } => [
                     self.primitives.int32,
                     self.primitives.int64,
@@ -259,7 +261,23 @@ impl Inferencer<'_> {
                 ]
                 .iter()
                 .any(|allowed_ty| self.unifier.unioned(ret_ty, *allowed_ty)),
-                TypeEnum::TTuple { ty, .. } => ty.iter().all(|t| self.check_return_value_ty(*t)),
+            
+                // For a tuple, first check that none of the elements are lists or NDArrays.
+                // Then, recursively ensure that each element is also a safe return type.
+                TypeEnum::TTuple { ty, .. } => {
+                    for &elem_ty in ty {
+                        if let TypeEnum::TObj { obj_id, .. } = &*self.unifier.get_ty_immutable(elem_ty) {
+                         // Here we try to get the concrete identifier of the object.
+                            if *obj_id == PrimDef::List.id() || *obj_id == PrimDef::NDArray.id() {
+                                return false;
+                            }       
+                        }
+                    }
+                    // Recursively check that all tuple element types are acceptable.
+                    ty.iter().all(|t| self.check_return_value_ty(*t))
+                },
+
+                // Any other type is disallowed.
                 _ => false,
             }   
         }