New ownership guide

[steveklabnik]

This is the start of the new "Ownership" guide, to replace the lifetimes guide.

I'm still working on it, but I wanted to share my progress, as this guide is very important, and I'd like as many eyes on it as possible. 😄

[steveklabnik]

I also only deprecated the old one 😉 ❤️ @huonw

[Manishearth]

Yay! I'll read through the whole thing when I get time. Couple of things:

• Could this guide also explain the difference between moved and copied types?
• It should probably discuss clone() too, and any other common errors and how to escape them

[richo]

typo, lifetime

[steveklabnik]

sigh

[steveklabnik]

@Manishearth move semantics aren't exactly the same thing as ownership. clone() is something that will end up being discussed, of course.

[Manishearth]

Hm, agreed, but I found them closely related. While learning Rust at first I didn't realize the difference between move/copy values and thus confused myself a lot. It took me a while to consolidate &/&mut, ~ (now box), clone, ref, and move/copy semantics and understand the memory model properly enough to use it without fighting the compiler. While they're theoretically something different, practically they turn up in similar places. But I guess discussing it elsewhere is okay, as long as they are discussed :)

[dodecaphonic]

SomeStrut -> SomeStruct?

[huonw]

move semantics aren't exactly the same thing as ownership

Ownership implies move semantics, and values moving are one of the major ways people hit ownership... they're intimately linked.

(e.g. taking a x: &T to y: T via y = *x requires taking the data out of x by value and placing it into y, which requires transferring ownership, cf. my answer here.)

[sellibitze]

That sounds like what lives in the heap is a Box<int>. But that's not true. In your case x living on the stack would be a Box<int>, a handle you can use to reach the heap-allocated int.