[lukaszwojtow]

I always prefer by-borrow. That's because in the future this struct may become non-copy and that means some unnecessary refactoring. My thinking is a bit like "don't take ownership if not needed" - the "not needed" part is the most important thing. Don't require things that are not needed.

[zozbot234]

If a struct might lose Copy you shouldn't implement Copy at all, to preserve forward compatibility. You can still derive Clone in most cases; using .clone() does not per se add any overhead.

[carlmr]

Exactly, and if performance at some point matters: benchmark!

And I would bet 9 times out of 10 it won't be the bottleneck or even make a measurable difference.

[QuadDamaged]

Exactly why IMHO the rust stdlib is so easy to understand. Ownership only when required as a design principle tends to make the design of the overall system more consistent / easier to approach.

[eterevsky]

If it's a 3D real-valued vector, or similarly basic structure, you can be fairly certain, that it will stay copyable.

[josephg]

I agree. Being copyable is part of the signature for something like this. Explicitly so in rust.

[theptip]

Rust noob here - is it common to see a struct lose Copy as things grow?

[sedatk]

> don't take ownership if not needed

That's my approach too as a Rust newbie. Borrow by default and take ownership only when needed, for the best ergononmics.