Add arity check to Obj.__call__/Obj::do_call

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/obj.rs

@@ -474,6 +474,23 @@ impl Obj {
                     .get_vtable_attr(obj_ptr.clone(), "__init__")
                     .expect("no __init__");
 
+                // check arity against __init__ function
+                // TODO Obj::do_call - need to throw an exception when __init__ arity does not
+                //                     match what was passed to __call__
+                //                     Also need to throw an exception when __init__ is not a
+                //                     function or doesn't have an arity
+                // BLOCKED-ON: exceptions
+                if let Some(arity) = init.borrow().arity() {
+                    if argc != arity as usize {
+                        todo!(
+                            "TODO - throw an exception when {}.__call__ argc does not match the __init__ arity",
+                            obj_ptr.borrow().ty_name()
+                        );
+                    }
+                } else {
+                    todo!("TODO - throw an exception when __init__ member does not have an arity or is not a function");
+                }
+
                 vm.push(obj_ptr);
                 vm.push(init.clone());
                 // duplicate arguments that were pushed to the frame