BmpDecoder::read_rect enters unreachable code

[mabysh]

This happens in image::load_rect function because BmpDecoder implementation of ImageDecoderExt trait provides seek_scanline parameter which looks like this: |_, _| unreachable!(). But it is reachable in runtime.

Expected

area of bmp image is read correctly by image::load_rect function

Actual behaviour

Process panics with error:

thread 'main::tests::decode_bmp' panicked at 'internal error: entered unreachable code', /home/byshnev/.cargo/registry/src/github.com-1ecc6299db9ec823/image-0.23.13/./src/codecs/bmp/decoder.rs:1470:84

Reproduction steps

    fn decode_bmp() {
        let f = File::open("path/to/any_rgba8.bmp").unwrap();
        let mut decoder = BmpDecoder::new(f).unwrap();

        let mut buf: Vec<u8> = vec![0; decoder.total_bytes() as usize];
        decoder.read_rect(0, 0, 8, 8, buf.as_bytes_mut()).unwrap(); // adjust width/height depending on image size
    }