title: Mismatched types, expected () found Result when using lookup_host
body: <p>I am using <a href="https://doc.rust-lang.org/std/net/fn.lookup_host.html">std::net::lookup_host</a>. When I build, an error occurs. I am using Rust 1.2.</p>
  
  <pre><code>use std::net;
  fn main() {
      for host in try!(net::lookup_host("rust-lang.org")) {
          println!("found address : {}", try!(host));
      }
  }
  </code></pre>
  
  <p>Error</p>
  
  <pre><code>&lt;std macros&gt;:5:8: 6:42 error: mismatched types:
   expected `()`,
      found `core::result::Result&lt;_, _&gt;`
  (expected (),
      found enum `core::result::Result`) [E0308]
  &lt;std macros&gt;:5 return $ crate:: result:: Result:: Err (
  &lt;std macros&gt;:6 $ crate:: convert:: From:: from ( err ) ) } } )
  &lt;std macros&gt;:1:1: 6:48 note: in expansion of try!
  exam.rs:4:14: 4:53 note: expansion site
  note: in expansion of for loop expansion
  exam.rs:4:2: 6:3 note: expansion site
  &lt;std macros&gt;:5:8: 6:42 help: run `rustc --explain E0308` to see a detailed explanation
  &lt;std macros&gt;:5:8: 6:42 error: mismatched types:
   expected `()`,
      found `core::result::Result&lt;_, _&gt;`
  (expected (),
      found enum `core::result::Result`) [E0308]
  &lt;std macros&gt;:5 return $ crate:: result:: Result:: Err (
  &lt;std macros&gt;:6 $ crate:: convert:: From:: from ( err ) ) } } )
  &lt;std macros&gt;:1:1: 6:48 note: in expansion of try!
  exam.rs:5:34: 5:44 note: expansion site
  note: in expansion of format_args!
  &lt;std macros&gt;:2:25: 2:56 note: expansion site
  &lt;std macros&gt;:1:1: 2:62 note: in expansion of print!
  &lt;std macros&gt;:3:1: 3:54 note: expansion site
  &lt;std macros&gt;:1:1: 3:58 note: in expansion of println!
  exam.rs:5:3: 5:46 note: expansion site
  note: in expansion of for loop expansion
  exam.rs:4:2: 6:3 note: expansion site
  &lt;std macros&gt;:5:8: 6:42 help: run `rustc --explain E0308` to see a detailed explanation
  error: aborting due to 2 previous errors
  </code></pre>