Rollup merge of #88031 - ibraheemdev:build-hasher-object-safe, r=m-ou-se

Make `BuildHasher` object safe

Resolves #87991

2 files changed, 12 insertions, 2 deletions

diff --git a/library/core/src/hash/mod.rs b/library/core/src/hash/mod.rs
index 510e233b431..77161e961e7 100644
--- a/library/core/src/hash/mod.rs
+++ b/library/core/src/hash/mod.rs
@@ -520,7 +520,10 @@ pub trait BuildHasher {
     /// );
     /// ```
     #[unstable(feature = "build_hasher_simple_hash_one", issue = "86161")]
-    fn hash_one<T: Hash>(&self, x: T) -> u64 {
+    fn hash_one<T: Hash>(&self, x: T) -> u64
+    where
+        Self: Sized,
+    {
         let mut hasher = self.build_hasher();
         x.hash(&mut hasher);
         hasher.finish()
diff --git a/library/core/tests/hash/mod.rs b/library/core/tests/hash/mod.rs
index 1566d357490..72ccdd4848a 100644
--- a/library/core/tests/hash/mod.rs
+++ b/library/core/tests/hash/mod.rs
@@ -1,7 +1,7 @@
 mod sip;
 
 use std::default::Default;
-use std::hash::{Hash, Hasher};
+use std::hash::{BuildHasher, Hash, Hasher};
 use std::rc::Rc;
 
 struct MyHasher {
@@ -139,3 +139,10 @@ fn test_indirect_hasher() {
     }
     assert_eq!(hasher.hash, 5);
 }
+
+#[test]
+fn test_build_hasher_object_safe() {
+    use std::collections::hash_map::{DefaultHasher, RandomState};
+
+    let _: &dyn BuildHasher<Hasher = DefaultHasher> = &RandomState::new();
+}