when used for non-blocking reads anyway. we've got this:

impl io::Read for Lock<'_, Nonblocking> {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        for byte in buf.iter_mut() {
            *byte = self.inner.read_nonblocking()?;
        }
        Ok(buf.len())
    }
}

but on trait mycelium_util::io::Read:

    /// # Errors
    ///
    /// If this function encounters any form of I/O or other error, an error
    /// variant will be returned. If an error is returned then it must be
    /// guaranteed that no bytes were read.

so if we're reading a buffer of size >1 and there's an error (say, no more data to read so you WouldBlock), we drop the read bytes on the floor. here i think we'd be ok by returning however many bytes were read until the WouldBlock, if that was the error, but i think in general we probably want a more verbose read() variant that always returns like, (usize, Result<(), Error>) or something. (i did exactly the same thing as myceium_util::io::Read's requirement in yaxpeax's reader type because posix brain lol)