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// run-pass
// Test that an `&mut self` method, when invoked on a place whose
// type is `&mut [u8]`, passes in a pointer to the place and not a
// temporary. Issue #19147.
use std::slice;
use std::cmp;
trait MyWriter {
fn my_write(&mut self, buf: &[u8]) -> Result<(), ()>;
}
impl<'a> MyWriter for &'a mut [u8] {
fn my_write(&mut self, buf: &[u8]) -> Result<(), ()> {
let amt = cmp::min(self.len(), buf.len());
self[..amt].clone_from_slice(&buf[..amt]);
let write_len = buf.len();
unsafe {
*self = slice::from_raw_parts_mut(
self.as_mut_ptr().add(write_len),
self.len() - write_len
);
}
Ok(())
}
}
fn main() {
let mut buf = [0; 6];
{
let mut writer: &mut [_] = &mut buf;
writer.my_write(&[0, 1, 2]).unwrap();
writer.my_write(&[3, 4, 5]).unwrap();
}
// If `my_write` is not modifying `buf` in place, then we will
// wind up with `[3, 4, 5, 0, 0, 0]` because the first call to
// `my_write()` doesn't update the starting point for the write.
assert_eq!(buf, [0, 1, 2, 3, 4, 5]);
}
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