ICE when calling method on trait object with incorrect self type

[jdm]

trait Foo {
    fn foo(~self);
}

impl Foo for int {
    fn foo(~self) {
    }
}

fn main() {
    (@5 as @Foo).foo();
}

error: internal compiler error: ~self receiver with non-~Trait

[catamorphism]

I thought maybe I could fix this quickly, but the interaction in typeck::check::method between auto-derefing and (the currently nonexistent checking of) non-@ traits is making my brain hurt. So, de-milestoning.

[catamorphism]

Reproduced in 0252c30 -- nominating for milestone 5, production-ready.

[graydon]

accepted for production-ready milestone

[nikomatsakis]

Almost certainly would be fixed by #5762

[graydon]

updated code example, still ICEs.

[jdm]

No more ICE:

/tmp/d.rs:11:4: 11:23 error: type `@Foo:'static` does not implement any method in scope named `foo`
/tmp/d.rs:11     (@5 as @Foo).foo();
                 ^~~~~~~~~~~~~~~~~~~
error: aborting due to previous error

Flagging as needstest.