There is a recurring issue with slow error printing. Here's a fine but reasonably slow command:
i1 : R = QQ[x];
i2 : M = coker random(R^1000, R^1000);
i3 : elapsedTime complex(apply(toList(0..10), i -> M));
-- .000228783s elapsed
But if you accidentally miss the "toList", it takes minutes only to get the error:
i4 : elapsedTime complex(apply((0..10), i -> M));
stdio:4:19:(3): error: no method found for applying complex to:
...