diff --git a/library/core/src/hash/mod.rs b/library/core/src/hash/mod.rs index 510e233b43110..77161e961e798 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(&self, x: T) -> u64 { + fn hash_one(&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 1566d35749017..72ccdd4848a47 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 = &RandomState::new(); +}