[masklinn]

> In fact, in general it's recommended not to use Box, because it complicates human reasoning about the code.

Really? I've always understood it was because when possible that decision should be left to the caller and boxing by default just made the interface less flexible/convenient for callers. How does Box complicate reasoning about the code?

[falcolas]

To me, because Boxed objects are a weird combination of a pointer and a stack value. Boxed values have a lifespan all their own, and you need to understand the details of a box's scope to understand how they will behave, and when they will be deallocated.