   InputEncoding : UnicodeCodec,
   OutputEncoding : UnicodeCodec
   where InputEncoding.CodeUnit == Input.Element
-  >(
+>(
   inputEncoding: InputEncoding.Type, _ outputEncoding: OutputEncoding.Type,
   _ input: Input, _ output: (OutputEncoding.CodeUnit) -> Void,
   stoppingOnError stopOnError: Bool
-  ) -> Bool {
-    fatalError("unavailable function can't be called")
+) -> Bool {
+  fatalError("unavailable function can't be called")
 }
 
 extension UTF16 {

    _precondition(width(x) == 2)
    return UTF16.CodeUnit(
      (x.value - 0x1_0000) & (((1 as UInt32) << 10) - 1)
      ) + 0xDC00
  }

  @warn_unused_result

    return UTF8.CodeUnit(utf16)
  }
}

extension UTF16 {
  /// Returns the number of code units required to encode `x`.
  @warn_unused_result
