 //
 //===----------------------------------------------------------------------===//
 
-// N.B.: This free function has been manually specialized below where
-// `UTF8CodeUnits == UnsafeBufferPoint<UInt8>`. Ensure that any changes are
-// made in sync.
 @_alwaysEmitIntoClient
-@inline(never)
-internal func _parseASCIIDigits<
-  UTF8CodeUnits: Collection, Result: FixedWidthInteger
->(
-  _ codeUnits: UTF8CodeUnits, radix: Int, isNegative: Bool
-) -> Result? where UTF8CodeUnits.Element == UInt8 {
+internal func _parseASCIIDigits<Result: FixedWidthInteger>(
+  _ codeUnits: UnsafeBufferPointer<UInt8>, radix: Int, isNegative: Bool
+) -> Result? {
   _internalInvariant(radix >= 2 && radix <= 36)
   guard _fastPath(!codeUnits.isEmpty) else { return nil }
   let multiplicand = Result(radix)

      radix: radix, isNegative: false)
  }
  return _parseASCIIDigits(codeUnits, radix: radix, isNegative: false)
}

extension FixedWidthInteger {

  return result
}

@_alwaysEmitIntoClient
internal func _parseASCII<Result: FixedWidthInteger>(
  _ codeUnits: UnsafeBufferPointer<UInt8>, radix: Int
