Small changes to fix documentation auto compile issues

src/libstd/net/tcp.rs

@@ -43,11 +43,12 @@
 /// use std::io::prelude::*;
 /// use std::net::TcpStream;
 ///
-/// {
+/// fn main() -> std::io::Result<()> {
 ///     let mut stream = TcpStream::connect("127.0.0.1:34254")?;
 ///
 ///     stream.write(&[1])?;
 ///     stream.read(&mut [0; 128])?;
+///     Ok(())
 /// } // the stream is closed here
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]