rust-lang/rust — pull request #16482 by pcwalton (2014-08-13 20:59:51+00:00)
Title: 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]

r? @brson