librustc: Make unqualified identifier searches terminate at the nearest module scope. r=tjc

src/libcore/util.rs

@@ -19,6 +19,7 @@ Miscellaneous helpers for common patterns.
 #[forbid(deprecated_pattern)];
 
 use cmp::Eq;
+use prelude::*;
 
 /// The identity function.
 #[inline(always)]
@@ -104,6 +105,10 @@ pub fn unreachable() -> ! {
 
 mod tests {
     #[legacy_exports];
+
+    use option::{None, Some};
+    use util::{NonCopyable, id, replace, swap};
+
     #[test]
     fn identity_crisis() {
         // Writing a test for the identity function. How did it come to this?