Inconsistency in whether methods of shadowed traits are usable

This compiles:

``` rust
mod foo {
    trait IntoIterator {}    
    fn f() { Some(0).into_iter(); }
}
```

but this doesn't:

``` rust
trait T {}
mod bar {
    use T as IntoIterator;
    fn f() { Some(0).into_iter(); }
}
```

More generally, a shadowed trait's methods are usable if it is shadowed by an item, but not if it is shadowed by an import.

Should methods from shadowed traits be usable?
