On 6/12/14 11:15 AM, Tommi wrote:
On 2014-06-12, at 20:59, Corey Richardson <[email protected]
<mailto:[email protected]>> wrote:
Implicit cloning is a non-starter. Clones can be very expensive.
Hiding that cost is undesirable and would require adding Clone to the
language (it's currently a normal library feature).
But I think it will be easy to make the error of writing the explicit
.clone() in places where it's not needed. For example:
fn foo<T>(value: T) {}
let x = box 123;
x.clone().foo();
x.clone().foo();
...given that `x` is not used after those lines, the last call to
.clone() is unnecessary. Whereas, if the task of cloning (implicitly) is
assigned to the compiler, then the compiler can use static analysis to
make sure such programming errors never occur. The example above would
become something like:
fn foo<T>(stable value: T) {}
let x = box 123;
x.foo(); // here `x` gets cloned here
x.foo(); // here `x` doesn't get cloned because this is the last use of `x`
We tried that in earlier versions of Rust. There were way too many clones.
Patrick
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