Rust import problems (valid as of 19dfec2)

ex1a.rs

// crate name requires an absolute path???? (non-working)
mod A { pub fn x() { core::io::stdout(); } }
fn main() { A::x(); }

ex1b.rs

// crate name requires an absolute path???? (working)
mod A { pub fn x() { ::core::io::stdout(); } }
fn main() { A::x(); }

ex2a.rs

// core::io shadowed by A::*???? (non-working)
mod A { }
use io::{ReaderUtil, WriterUtil};
use A::*;
fn main() { }

ex2b.rs

// core::io shadowed by A::*???? (working)
mod A { }
use A::*;
use io::{ReaderUtil, WriterUtil};
fn main() { }