   private var _core: Core
 
   @inline(__always)
-  internal init(seed: (UInt64, UInt64)) {
+  internal init(seed: Hasher._Seed) {
     self._buffer = _HasherTailBuffer()
     self._core = Core(seed: seed)
   }

  /// This comes handy when type's _hash(into:) implementation needs to perform
  /// one-shot hashing for some of its components. (E.g., for commutative
  /// hashing.)
  func _generateSeed() -> (UInt64, UInt64)
}

@inline(__always)

  @_effects(readnone)
  @usableFromInline
  internal static func _hash(
    seed: _Seed,
    bytes: UnsafeRawBufferPointer) -> Int {
    var core = Core(seed: seed)
    core.combine(bytes: bytes)
