Struct std::io::WriterPanicked

use std::io::{self, BufWriter, Write};
use std::panic::{catch_unwind, AssertUnwindSafe};

struct PanickingWriter;
impl Write for PanickingWriter {
  fn write(&mut self, buf: &[u8]) -> io::Result<usize> { panic!() }
  fn flush(&mut self) -> io::Result<()> { panic!() }
}

let mut stream = BufWriter::new(PanickingWriter);
write!(stream, "some data").unwrap();
let result = catch_unwind(AssertUnwindSafe(|| {
    stream.flush().unwrap()
}));
assert!(result.is_err());
let (recovered_writer, buffered_data) = stream.into_parts();
assert!(matches!(recovered_writer, PanickingWriter));
assert_eq!(buffered_data.unwrap_err().into_inner(), b"some data");