Rollup merge of #47510 - sfackler:deprecate-dns, r=alexcrichton

Deprecate std::net::lookup_host

We intended to do this quite a while ago but it snuck through.

r? @alexcrichton

Author: GuillaumeGomez

src/libstd/net/addr.rs

@@ -12,7 +12,9 @@ use fmt;
 use hash;
 use io;
 use mem;
-use net::{lookup_host, ntoh, hton, IpAddr, Ipv4Addr, Ipv6Addr};
+use net::{ntoh, hton, IpAddr, Ipv4Addr, Ipv6Addr};
+#[allow(deprecated)]
+use net::lookup_host;
 use option;
 use sys::net::netc as c;
 use sys_common::{FromInner, AsInner, IntoInner};
@@ -845,6 +847,7 @@ impl ToSocketAddrs for (Ipv6Addr, u16) {
     }
 }
 
+#[allow(deprecated)]
 fn resolve_socket_addr(s: &str, p: u16) -> io::Result<vec::IntoIter<SocketAddr>> {
     let ips = lookup_host(s)?;
     let v: Vec<_> = ips.map(|mut a| { a.set_port(p); a }).collect();

src/libstd/net/mod.rs

@@ -134,12 +134,15 @@ fn each_addr<A: ToSocketAddrs, F, T>(addr: A, mut f: F) -> io::Result<T>
                                               iterator and returning socket \
                                               addresses",
            issue = "27705")]
+#[rustc_deprecated(since = "1.25", reason = "Use the ToSocketAddrs trait instead")]
 pub struct LookupHost(net_imp::LookupHost);
 
 #[unstable(feature = "lookup_host", reason = "unsure about the returned \
                                               iterator and returning socket \
                                               addresses",
            issue = "27705")]
+#[rustc_deprecated(since = "1.25", reason = "Use the ToSocketAddrs trait instead")]
+#[allow(deprecated)]
 impl Iterator for LookupHost {
     type Item = SocketAddr;
     fn next(&mut self) -> Option<SocketAddr> { self.0.next() }
@@ -149,6 +152,8 @@ impl Iterator for LookupHost {
                                               iterator and returning socket \
                                               addresses",
            issue = "27705")]
+#[rustc_deprecated(since = "1.25", reason = "Use the ToSocketAddrs trait instead")]
+#[allow(deprecated)]
 impl fmt::Debug for LookupHost {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.pad("LookupHost { .. }")
@@ -181,6 +186,8 @@ impl fmt::Debug for LookupHost {
                                               iterator and returning socket \
                                               addresses",
            issue = "27705")]
+#[rustc_deprecated(since = "1.25", reason = "Use the ToSocketAddrs trait instead")]
+#[allow(deprecated)]
 pub fn lookup_host(host: &str) -> io::Result<LookupHost> {
     net_imp::lookup_host(host).map(LookupHost)
 }