rust-lang/rust — pull request #15352 by pcwalton (2014-07-02 20:30:33+00:00)
Title: librustc: Have the kind checker check sub-bounds in trait casts.

This can break code that looked like:

struct S {
val: T,
}
trait Gettable {
...
}
impl Gettable for S {
...
}
let t: Box> = box S {
val: "one".to_string(),
};
let a = t as Box>;
// ^ note no `Copy` bound

Change this code to:

impl Gettable for S {
// ^ remove `Copy` bound
...
}

Closes #14061.

[breaking-change]

r? @nick29581