.clone() on Vec<T> returns &[T] when T does not implement Clone

[JustAPerson]

fn main() {
    struct Test;
    let v = vec![Test];
    let w: Vec<Test> = v.clone();
}

<anon>:4:24: 4:33 error: mismatched types: expected `collections::vec::Vec<main::Test>`, found `&[main::Test]` (expected struct collections::vec::Vec, found &-ptr)
<anon>:4     let w: Vec<test> = v.clone();

The solution to this error is to derive the Clone trait for Test.

Since Vec<Test> does not implement Clone trait, Vec<Test> is automatically coerced to &[Test], which does implement Clone, by way of the Deref trait.

This behavior and error are unintuitive. Perhaps better information could be reported here.

[aturon]

cc me

[aturon]

cc @nikomatsakis @alexcrichton This is an interesting downside of making Vec deref...

[JustAPerson]

This issue may be closed now. On nightly builds, a reasonable error is given and the unexpected behavior no longer occurs.

<anon>:4:26: 4:33 error: type `collections::vec::Vec<main::Test>` does not implement any method in scope named `clone`
<anon>:4     let w: Vec<Test> = v.clone();
                                  ^~~~~~~
<anon>:4:33: 4:33 help: methods from traits can only be called if the trait is implemented and in scope; the following trait defines a method `clone`, perhaps you need to implement it:
<anon>:4:33: 4:33 help: candidate #1: `core::clone::Clone`
error: aborting due to previous error
playpen: application terminated with error code 101