`std::io::Chain` could implement BufRead

[troplin]

The implementation is straight forward:

impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> {
    fn fill_buf(&mut self) -> Result<&[u8]> {
        if !self.done_first {
            match try!(self.first.fill_buf()) {
                buf if buf.len() == 0 => { self.done_first = true; }
                buf => return Ok(buf),
            }
        }
        self.second.fill_buf()
    }
    fn consume(&mut self, amt: usize) {
        if !self.done_first {
            self.first.consume(amt)
        } else {
            self.second.consume(amt)
        }
    }
}

Or am I overlooking something?

[rphmeier]

std::net::Chain -> std::io::Chain?

Now that the ? operator has landed, I would guess that would be favored over try! in std.
The tricky thing about trait implementations is that they become insta-stable, so it's usually good to be apprehensive of adding new ones. This one seems uncontroversial, so it's likely that it may have just been overlooked previously.

[troplin]

Whoops, yes.
I've changed the title.

The implementation is not set in stone of course.

[sfackler]

This seems reasonable I think - want to open a PR?

[troplin]

I'll give it a try. I'm still learning how to everything works with github...

[troplin]

@rphmeier you mentioned that it will be insta-stable. Does that mean that I have to tag it as stable for my PR?

#[stable(feature = "rust1", since = "1.9.0")]

Like that?

[sfackler]

Yep, though you can't use the rust1 feature since feature names are tied to a specific release. Just make one up though - chain_buf_read or whatever.

[Aatch]

Closed by #32541