Fix warnings

Author: Aaron1011

compiler/rustc_data_structures/src/stable_hasher.rs

@@ -449,7 +449,7 @@ impl<K: HashStableEq + Eq + Hash, V: HashStableEq, R: BuildHasher> HashStableEq
 }
 
 impl<T> HashStableEq for std::marker::PhantomData<T> {
-    fn hash_stable_eq(&self, other: &Self) -> bool {
+    fn hash_stable_eq(&self, _other: &Self) -> bool {
         true
     }
 }

compiler/rustc_index/src/bit_set.rs

@@ -7,7 +7,7 @@ use std::mem;
 use std::ops::{BitAnd, BitAndAssign, BitOrAssign, Bound, Not, Range, RangeBounds, Shl};
 use std::slice;
 
-use rustc_macros::{Decodable, Encodable, HashStableEq};
+use rustc_macros::{Decodable, Encodable};
 
 #[cfg(test)]
 mod tests;