librustc: Forbid external crates, imports, and/or items from being

declared with the same name in the same scope.

This breaks several common patterns. First are unused imports:

    use foo::bar;
    use baz::bar;

Change this code to the following:

    use baz::bar;

Second, this patch breaks globs that import names that are shadowed by
subsequent imports. For example:

    use foo::*; // including `bar`
    use baz::bar;

Change this code to remove the glob:

    use foo::{boo, quux};
    use baz::bar;

Or qualify all uses of `bar`:

    use foo::{boo, quux};
    use baz;

    ... baz::bar ...

Finally, this patch breaks code that, at top level, explicitly imports
`std` and doesn't disable the prelude.

    extern crate std;

Because the prelude imports `std` implicitly, there is no need to
explicitly import it; just remove such directives.

The old behavior can be opted into via the `import_shadowing` feature
gate. Use of this feature gate is discouraged.

This implements RFC #116.

Closes #16464.

[breaking-change]

1 files changed, 1 insertions, 6 deletions

diff --git a/src/libstd/io/net/unix.rs b/src/libstd/io/net/unix.rs
index d88af8dd30a..eb251075418 100644
--- a/src/libstd/io/net/unix.rs
+++ b/src/libstd/io/net/unix.rs
@@ -26,12 +26,7 @@ instances as clients.
 
 use prelude::*;
 
-use c_str::ToCStr;
-use clone::Clone;
-use io::{Listener, Acceptor, Reader, Writer, IoResult, IoError};
-use io::{standard_error, TimedOut};
-use kinds::Send;
-use boxed::Box;
+use io::{Listener, Acceptor, IoResult, IoError, TimedOut, standard_error};
 use rt::rtio::{IoFactory, LocalIo, RtioUnixListener};
 use rt::rtio::{RtioUnixAcceptor, RtioPipe};
 use time::Duration;