2 files changed, 4 insertions, 4 deletions
diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index 6dc044a6d38..598409c9051 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -1,7 +1,9 @@
 use std::marker::PhantomData;
+#[cfg(not(feature = "nightly"))]
+use std::mem;
 use std::ops::{BitAnd, BitAndAssign, BitOrAssign, Bound, Not, Range, RangeBounds, Shl};
 use std::rc::Rc;
-use std::{fmt, iter, mem, slice};
+use std::{fmt, iter, slice};
 
 use Chunk::*;
 #[cfg(feature = "nightly")]
@@ -14,7 +16,7 @@ use crate::{Idx, IndexVec};
 mod tests;
 
 type Word = u64;
-const WORD_BYTES: usize = mem::size_of::<Word>();
+const WORD_BYTES: usize = size_of::<Word>();
 const WORD_BITS: usize = WORD_BYTES * 8;
 
 // The choice of chunk size has some trade-offs.
diff --git a/compiler/rustc_index/src/vec/tests.rs b/compiler/rustc_index/src/vec/tests.rs
index 381d79c24fc..5b0ca4b2b92 100644
--- a/compiler/rustc_index/src/vec/tests.rs
+++ b/compiler/rustc_index/src/vec/tests.rs
@@ -9,8 +9,6 @@ crate::newtype_index! {
 
 #[test]
 fn index_size_is_optimized() {
-    use std::mem::size_of;
-
     assert_eq!(size_of::<MyIdx>(), 4);
     // Uses 0xFFFF_FFFB
     assert_eq!(size_of::<Option<MyIdx>>(), 4);