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, 0 insertions, 1 deletions

diff --git a/src/libstd/num/f64.rs b/src/libstd/num/f64.rs
index 3180ee28c6f..d8d118a6721 100644
--- a/src/libstd/num/f64.rs
+++ b/src/libstd/num/f64.rs
@@ -21,7 +21,6 @@ use intrinsics;
 use libc::c_int;
 use num::strconv;
 use num;
-use string::String;
 
 pub use core::f64::{RADIX, MANTISSA_DIGITS, DIGITS, EPSILON, MIN_VALUE};
 pub use core::f64::{MIN_POS_VALUE, MAX_VALUE, MIN_EXP, MAX_EXP, MIN_10_EXP};