message: Make compression enum non-exhaustive
diff: @@ -215,7 +215,7 @@ pub struct PNGEncoder<W: Write> {
  pub enum CompressionType {
  /// Default compression level
  Default,
  - /// Fast minimal compression
  + /// Fast, minimal compression
  Fast,
  /// High compression level
  Best,
  @@ -223,6 +223,9 @@ pub enum CompressionType {
  Huffman,
  /// Run-length encoding compression
  Rle,
  +
  + #[doc(hidden)]
  + __NonExhaustive(crate::utils::NonExhaustiveMarker),
  }
  /// Filter algorithms used to process image data to improve compression. The
  @@ -290,6 +293,7 @@ impl<W: Write> PNGEncoder<W> {
  CompressionType::Best => png::Compression::Best,
  CompressionType::Huffman => png::Compression::Huffman,
  CompressionType::Rle => png::Compression::Rle,
  + CompressionType::__NonExhaustive(marker) => match marker._private {},
  };
  let filt = match self.filter {
  FilterType::NoFilter => png::FilterType::NoFilter,
  