for loop over trait that inherits Iterator gives error

[detzgk]

If a trait inherits Iterator, it used to be (rust-0.11) usable as the expression in a for loop. In recent nightlies (a1429bc 2014-08-08 21:36:11 +0000) this seems to be broken.

pub trait Foo : Iterator<int> {
}

fn main() {
    let f : &Foo;
    for item in f {
    }
}

This gives me:

test.rs:6:14: 6:15 error: for loop expression does not implement the Iterator trait
test.rs:6 for i in f {

[detzgk]

sfackler on IRC says some work was done on for loops recently.
/cc @pcwalton

[alexcrichton]

I believe that this is technically correct as the trait object &Foo does not implement the Iterator trait. This is similar to how the Writer trait is not implemented for &mut Writer, but rather there is a manual implementation for it. The fix you'll need is impl<'a> Iterator<int> for &'a Foo { /* ... */ }

For now, however, this is working as intended, so I'm going to close this.