collections::vec::IntoIter is not Send + confusing error message

[renato-zannon]

The IntoIter iterator on Vecs (and possibly other collections, though I haven't checked) isn't Send anymore, even though I think it could be - it seems to drop the remaining elements and deallocate the memory when dropped, and doesn't refer to anything on the stack.

Reproduction:

fn main() {
    let vec = vec![1, 2, 3];
    typecheck_me(vec.into_iter());
}

fn typecheck_me<T>(_: T) where T: Send {}

The program above produces following error message when compiled:

sender.rs:3:5: 3:17 error: the trait `core::marker::Send` is not implemented for the type `*mut _`
sender.rs:3     typecheck_me(vec.into_iter());
                ^~~~~~~~~~~~
sender.rs:3:5: 3:17 error: the trait `core::marker::Send` is not implemented for the type `*const _`
sender.rs:3     typecheck_me(vec.into_iter());

Which is not very helpful, especially when IntoIter is several levels deep on the object being sent (which was my case)

[Gankra]

IntoIter should just be as Send as Vec. Feel free to send a PR to ammend this.