auto merge of #19511 : eddyb/rust/no-shadow, r=alexcrichton

r? @erickt

Author: bors

src/libcollections/bench.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::prelude::*;
+use prelude::*;
 use std::rand;
 use std::rand::Rng;
 use test::Bencher;

src/libcollections/binary_heap.rs

@@ -617,10 +617,9 @@ impl<T: Ord> Extend<T> for BinaryHeap<T> {
 
 #[cfg(test)]
 mod tests {
-    use std::prelude::*;
+    use prelude::*;
 
     use super::BinaryHeap;
-    use vec::Vec;
 
     #[test]
     fn test_iterator() {