message: improve type and depth reporting for Mat
diff: @@ -16,7 +16,7 @@ pub trait DataType: Copy + private::Sealed {
  macro_rules! data_type {
  ($rust_type: ty, $mat_depth: expr, $channels: expr) => {
  - impl DataType for $rust_type {
  + impl $crate::core::DataType for $rust_type {
  #[inline(always)]
  fn depth() -> i32 { $mat_depth }
  @@ -78,7 +78,7 @@ impl Mat {
  if mat_type == out_type {
  Ok(())
  } else {
  - Err(Error::new(core::StsUnmatchedFormats, format!("Mat type is: {}, but requested type is: {}", mat_type, out_type)))
  + Err(Error::new(core::StsUnmatchedFormats, format!("Mat type is: {}, but requested type is: {}", core::type_to_string(mat_type)?, core::type_to_string(out_type)?)))
  }
  }
  @@ -284,17 +284,17 @@ impl Mat {
  impl fmt::Debug for Mat {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  f.debug_struct("Mat")
  - .field("type", &self.typ().map_err(|_| fmt::Error)?)
  + .field("type", &self.typ().and_then(core::type_to_string).map_err(|_| fmt::Error)?)
  + .field("flags", &self.flags().map_err(|_| fmt::Error)?)
  .field("channels", &self.channels().map_err(|_| fmt::Error)?)
  - .field("depth", &self.depth().map_err(|_| fmt::Error)?)
  + .field("depth", &self.depth().and_then(core::depth_to_string).map_err(|_| fmt::Error)?)
  .field("dims", &self.dims().map_err(|_| fmt::Error)?)
  - .field("flags", &self.flags().map_err(|_| fmt::Error)?)
  - .field("elem_size", &self.elem_size().map_err(|_| fmt::Error)?)
  - .field("elem_size1", &self.elem_size1().map_err(|_| fmt::Error)?)
  - .field("total", &self.total().map_err(|_| fmt::Error)?)
  .field("size", &self.size().map_err(|_| fmt::Error)?)
  .field("rows", &self.rows().map_err(|_| fmt::Error)?)
  .field("cols", &self.cols().map_err(|_| fmt::Error)?)
  + .field("elem_size", &self.elem_size().map_err(|_| fmt::Error)?)
  + .field("elem_size1", &self.elem_size1().map_err(|_| fmt::Error)?)
  + .field("total", &self.total().map_err(|_| fmt::Error)?)
  .field("is_continuous", &self.is_continuous().map_err(|_| fmt::Error)?)
  .field("is_submatrix", &self.is_submatrix().map_err(|_| fmt::Error)?)
  .finish()
  