Supertrait methods are called on inner type of object type rather than any explicit impl for the object type

[huonw]

trait Foo: Clone {
    fn clone_as_obj(&self) -> ~Foo {
        ~(self.clone()) as ~Foo
    }
}

impl Clone for ~Foo {
    fn clone(&self) -> ~Foo {
        self.clone_as_obj();
    }
}

fn test(x: ~Foo) {
    x.clone();
}

clone-abort-3.rs:14:4: 14:14 error: cannot call a method whose type contains a self-type through an object
clone-abort-3.rs:14     x.clone();
                        ^~~~~~~~~~
error: aborting due to previous error
task 'rustc' failed at 'explicit failure', /home/huon/rust/src/libsyntax/diagnostic.rs:102
task '<main>' failed at 'explicit failure', /home/huon/rust/src/librustc/lib.rs:395

It seems like that should prefer the (~Foo).clone() method rather than trying to call the .clone that the compiler knows that the inner type must have.

[huonw]

cc @nikomatsakis (I guess).

[nikomatsakis]

That is not how method resolution works. Object methods are preferred (for various reasons, among them that otherwise you cannot impl Trait for ~Trait). Eventually universal method call syntax should allow you to be explicit for now you can write:

fn Clone<T:Clone>(x: T) { x.clone() }

and then

Clone(x)

instead of x.clone()

[nikomatsakis]

Closing because it is behaving as expected.