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Trim a bit of detail out of explanation of Copy; point to traits

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Carol (Nichols || Goulding) 2016-08-02 16:15:39 -04:00
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src/ch04-01-ownership.md
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@ -306,23 +306,15 @@ there’s no difference between deep and shallow copying here, so calling
we can leave it out. we can leave it out.
Rust has a special annotation that you can place on types like these, and that Rust has a special annotation that you can place on types like these, and that
annotation is called `Copy`. If a type is `Copy`, an older binding is still annotation is the `Copy` trait. We'll talk more about traits in Chapter XX. If
usable after assignment. Integers are an example of such a type; most of the a type has the `Copy` trait, an older binding is still usable after assignment.
primitive types are `Copy`. Rust will not let you make something have the `Copy` trait if it has
While we haven’t talked about how to mark a type as `Copy` yet, you might ask
yourself “what happens if we made `String` `Copy`?” The answer is you cannot.
Remember `drop()`? Rust will not let you make something `Copy` if it has
implemented `drop()`. If you need to do something special when the value goes implemented `drop()`. If you need to do something special when the value goes
out of scope, being `Copy` will be an error. out of scope, being `Copy` will be an error.
So what types are `Copy`? You can check the documentation for the given type to So what types are `Copy`? You can check the documentation for the given type to
be sure, but as a rule of thumb, any group of simple scalar values can be Copy, be sure, but as a rule of thumb, any group of simple scalar values can be Copy,
but nothing that requires allocation or is some form of resource is `Copy`. And but nothing that requires allocation or is some form of resource is `Copy`. Here’s some of the types that are `Copy`:
you can’t get it wrong: the compiler will throw an error if you incorrectly try
to use a type that moves, as we saw above.
Here’s some types that are `Copy`:
* All of the integer types, like `u32`. * All of the integer types, like `u32`.
* The booleans, `true` and `false`. * The booleans, `true` and `false`.