[jedisct1]

Is it still zero cost if the price to pay is a steep increase of code complexity?

The current model also still requires a lot of boxing and cloning, so it is far from being “zero cost” as advertised.

[steveklabnik]

> Is it still zero cost if the price to pay is a steep increase of code complexity?

Yes, because the "cost" in "zero-cost" only refers to runtime cost.