   /// Initialize a new hasher using the specified seed value.
   @usableFromInline
   @_effects(releasenone)
-  internal init(_seed seed: (UInt64, UInt64)) {
+  internal init(_seed seed: _Seed) {
     self._core = Core(seed: seed)
   }
 

  @_effects(readnone)
  @usableFromInline
  internal static func _hash(
    seed: (UInt64, UInt64),
    bytes value: UInt64,
    count: Int) -> Int {
    _sanityCheck(count >= 0 && count < 8)

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