Trait objects cannot call methods that take self by-value

[lilyball]

As was brought up in this reddit post, Trait objects cannot call methods that take self by-value. Even worse, the error message erroneously claims the desired method does not exist.

It seems to me that trait objects of the form ~Trait should work with self-by-value methods. And trait objects of the form &Trait should produce an appropriate error message (just like calling the same method on a reference does).

Example:

trait Foo {
    fn foo(self) -> int;
}

struct Bar;
impl Foo for Bar {
    fn foo(self) -> int { 42i }
}

fn main() {
    let bar = ~Bar as ~Foo;
    let _x: int = bar.foo();
}

This produces:

Untitled.rs:12:19: 12:28 error: type `~Foo:Send` does not implement any method in scope named `foo`
Untitled.rs:12     let _x: int = bar.foo();
                                 ^~~~~~~~~

[sfackler]

Dup of #10672

[lilyball]

@sfackler Thanks. I tried to find a pre-existing issue, and was surprised when I couldn't, but github's search really sucks.