Ah, neat! I think the last time I looked you couldn't, but it was ages ago; I'm not surprised to have misremembered and even less surprised if it's changed. I

Ah, neat! I think the last time I looked you couldn't, but it was ages ago; I'm not surprised to have misremembered and even less surprised if it's changed. Is it possible to provide a map method that re-throws whatever is thrown by its argument, without widening?