1 files changed, 22 insertions, 0 deletions
diff --git a/third_party/rust/precomputed-hash/src/lib.rs b/third_party/rust/precomputed-hash/src/lib.rs
new file mode 100644
index 0000000000..9cdb45d5b2
--- /dev/null
+++ b/third_party/rust/precomputed-hash/src/lib.rs
@@ -0,0 +1,22 @@
+//! A base trait to expose a precomputed hash for a type.
+
+/// A trait to expose a precomputed hash for a type.
+pub trait PrecomputedHash {
+    // TODO(emilio): Perhaps an associated type would be on point here.
+
+    /// Return the precomputed hash for this item.
+    fn precomputed_hash(&self) -> u32;
+}
+
+// These are equivalent to the `std::Hash` impls.
+impl<'a, T: PrecomputedHash> PrecomputedHash for &'a T {
+    fn precomputed_hash(&self) -> u32 {
+        (**self).precomputed_hash()
+    }
+}
+
+impl<'a, T: PrecomputedHash> PrecomputedHash for &'a mut T {
+    fn precomputed_hash(&self) -> u32 {
+        (**self).precomputed_hash()
+    }
+}