Seal ToSocketAddrs methods with an internal argument (#2892)

Closes #2891 

6 files changed, 43 insertions, 30 deletions

diff --git a/tokio/src/net/addr.rs b/tokio/src/net/addr.rs
index ed00ca4a..86b0962b 100644
--- a/tokio/src/net/addr.rs
+++ b/tokio/src/net/addr.rs
@@ -23,6 +23,14 @@ pub trait ToSocketAddrs: sealed::ToSocketAddrsPriv {}
 
 type ReadyFuture<T> = future::Ready<io::Result<T>>;
 
+#[cfg(any(feature = "dns", feature = "tcp", feature = "udp"))]
+pub(crate) fn to_socket_addrs<T>(arg: T) -> T::Future
+where
+    T: ToSocketAddrs,
+{
+    arg.to_socket_addrs(sealed::Internal)
+}
+
 // ===== impl &impl ToSocketAddrs =====
 
 impl<T: ToSocketAddrs + ?Sized> ToSocketAddrs for &T {}
@@ -34,8 +42,8 @@ where
     type Iter = T::Iter;
     type Future = T::Future;
 
-    fn to_socket_addrs(&self) -> Self::Future {
-        (**self).to_socket_addrs()
+    fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
+        (**self).to_socket_addrs(sealed::Internal)
     }
 }
 
@@ -47,7 +55,7 @@ impl sealed::ToSocketAddrsPriv for SocketAddr {
     type Iter = std::option::IntoIter<SocketAddr>;
     type Future = ReadyFuture<Self::Iter>;
 
-    fn to_socket_addrs(&self) -> Self::Future {
+    fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
         let iter = Some(*self).into_iter();
         future::ok(iter)
     }
@@ -61,8 +69,8 @@ impl sealed::ToSocketAddrsPriv for SocketAddrV4 {
     type Iter = std::option::IntoIter<SocketAddr>;
     type Future = ReadyFuture<Self::Iter>;
 
-    fn to_socket_addrs(&self) -> Self::Future {
-        SocketAddr::V4(*self).to_socket_addrs()
+    fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
+        SocketAddr::V4(*self).to_socket_addrs(sealed::Internal)
     }
 }
 
@@ -74,8 +82,8 @@ impl sealed::ToSocketAddrsPriv for SocketAddrV6 {
     type Iter = std::option::IntoIter<SocketAddr>;
     type Future = ReadyFuture<Self::Iter>;
 
-    fn to_socket_addrs(&self) -> Self::Future {
-        SocketAddr::V6(*self).to_socket_addrs()
+    fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
+        SocketAddr::V6(*self).to_socket_addrs(sealed::Internal)
     }
 }
 
@@ -87,7 +95,7 @@ impl sealed::ToSocketAddrsPriv for (IpAddr, u16) {
     type Iter = std::option::IntoIter<SocketAddr>;
     type Future = ReadyFuture<Self::Iter>;
 
-    fn to_socket_addrs(&self) -> Self::Future {
+    fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
         let iter = Some(SocketAddr::from(*self)).into_iter();
         future::ok(iter)
     }
@@ -101,9 +109,9 @@ impl sealed::ToSocketAddrsPriv for (Ipv4Addr, u16) {
     type Iter = std::option::IntoIter<SocketAddr>;
     type Future = ReadyFuture<Self::Iter>;
 
-    fn to_socket_addrs(&self) -> Self::Future {
+    fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
         let (ip, port) = *self;
-        SocketAddrV4::new(ip, port).to_socket_addrs()
+        SocketAddrV4::new(ip, port).to_socket_addrs(sealed::Internal)
     }
 }
 
@@ -115,9 +123,9 @@ impl sealed::ToSocketAddrsPriv for (Ipv6Addr, u16) {
     type Iter = std::option::IntoIter<SocketAddr>;
     type Future = ReadyFuture<Self::Iter>;
 
-    fn to_socket_addrs(&self) -> Self::Future {
+    fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
         let (ip, port) = *self;
-        SocketAddrV6::new(ip, port, 0, 0).to_socket_addrs()
+        SocketAddrV6::new(ip, port, 0, 0).to_socket_addrs(sealed::Internal)
     }
 }
 
@@ -129,7 +137,7 @@ impl sealed::ToSocketAddrsPriv for &[SocketAddr] {
     type Iter = std::vec::IntoIter<SocketAddr>;
     type Future = ReadyFuture<Self::Iter>;
 
-    fn to_socket_addrs(&self) -> Self::Future {
+    fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
         let iter = self.to_vec().into_iter();
         future::ok(iter)
     }
@@ -144,7 +152,7 @@ cfg_dns! {
         type Iter = sealed::OneOrMore;
         type Future = sealed::MaybeReady;
 
-        fn to_socket_addrs(&self) -> Self::Future {
+        fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
             use crate::runtime::spawn_blocking;
             use sealed::MaybeReady;
 
@@ -172,7 +180,7 @@ cfg_dns! {
         type Iter = sealed::OneOrMore;
         type Future = sealed::MaybeReady;
 
-        fn to_socket_addrs(&self) -> Self::Future {
+        fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
             use crate::runtime::spawn_blocking;
             use sealed::MaybeReady;
 
@@ -209,8 +217,8 @@ cfg_dns! {
         type Iter = sealed::OneOrMore;
         type Future = sealed::MaybeReady;
 
-        fn to_socket_addrs(&self) -> Self::Future {
-            (self.0.as_str(), self.1).to_socket_addrs()
+        fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
+            (self.0.as_str(), self.1).to_socket_addrs(sealed::Internal)
         }
     }
 
@@ -222,8 +230,8 @@ cfg_dns! {
         type Iter = <str as sealed::ToSocketAddrsPriv>::Iter;
         type Future = <str as sealed::ToSocketAddrsPriv>::Future;
 
-        fn to_socket_addrs(&self) -> Self::Future {
-            (&self[..]).to_socket_addrs()
+        fn to_socket_addrs(&self, _: sealed::Internal) -> Self::Future {
+            (&self[..]).to_socket_addrs(sealed::Internal)
         }
     }
 }
@@ -251,9 +259,12 @@ pub(crate) mod sealed {
         type Iter: Iterator<Item = SocketAddr> + Send + 'static;
         type Future: Future<Output = io::Result<Self::Iter>> + Send + 'static;
 
-        fn to_socket_addrs(&self) -> Self::Future;
+        fn to_socket_addrs(&self, internal: Internal) -> Self::Future;
     }
 
+    #[allow(missing_debug_implementations)]
+    pub struct Internal;
+
     cfg_dns! {
         #[doc(hidden)]
         #[derive(Debug)]
diff --git a/tokio/src/net/lookup_host.rs b/tokio/src/net/lookup_host.rs
index 3098b463..150228b5 100644
--- a/tokio/src/net/lookup_host.rs
+++ b/tokio/src/net/lookup_host.rs
@@ -1,5 +1,5 @@
 cfg_dns! {
-    use crate::net::addr::ToSocketAddrs;
+    use crate::net::addr::{self, ToSocketAddrs};
 
     use std::io;
     use std::net::SocketAddr;
@@ -33,6 +33,6 @@ cfg_dns! {
     where
         T: ToSocketAddrs
     {
-        host.to_socket_addrs().await
+        addr::to_socket_addrs(host).await
     }
 }
diff --git a/tokio/src/net/mod.rs b/tokio/src/net/mod.rs
index da6ad1fc..e3fb2c73 100644
--- a/tokio/src/net/mod.rs
+++ b/tokio/src/net/mod.rs
@@ -23,6 +23,8 @@
 //! [`UnixDatagram`]: UnixDatagram
 
 mod addr;
+#[cfg(any(feature = "tcp", feature = "udp"))]
+pub(crate) use addr::to_socket_addrs;
 pub use addr::ToSocketAddrs;
 
 cfg_dns! {
diff --git a/tokio/src/net/tcp/listener.rs b/tokio/src/net/tcp/listener.rs
index 323b8bca..ef0a87c0 100644
--- a/tokio/src/net/tcp/listener.rs
+++ b/tokio/src/net/tcp/listener.rs
@@ -1,7 +1,7 @@
 use crate::future::poll_fn;
 use crate::io::PollEvented;
 use crate::net::tcp::{Incoming, TcpStream};
-use crate::net::ToSocketAddrs;
+use crate::net::{to_socket_addrs, ToSocketAddrs};
 
 use std::convert::TryFrom;
 use std::fmt;
@@ -130,7 +130,7 @@ impl TcpListener {
     /// }
     /// ```
     pub async fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
-        let addrs = addr.to_socket_addrs().await?;
+        let addrs = to_socket_addrs(addr).await?;
 
         let mut last_err = None;
 
diff --git a/tokio/src/net/tcp/stream.rs b/tokio/src/net/tcp/stream.rs
index 4bf17449..99f77d41 100644
--- a/tokio/src/net/tcp/stream.rs
+++ b/tokio/src/net/tcp/stream.rs
@@ -2,7 +2,7 @@ use crate::future::poll_fn;
 use crate::io::{AsyncRead, AsyncWrite, PollEvented, ReadBuf};
 use crate::net::tcp::split::{split, ReadHalf, WriteHalf};
 use crate::net::tcp::split_owned::{split_owned, OwnedReadHalf, OwnedWriteHalf};
-use crate::net::ToSocketAddrs;
+use crate::net::{to_socket_addrs, ToSocketAddrs};
 
 use std::convert::TryFrom;
 use std::fmt;
@@ -116,7 +116,7 @@ impl TcpStream {
     /// [`write_all`]: fn@crate::io::AsyncWriteExt::write_all
     /// [`AsyncWriteExt`]: trait@crate::io::AsyncWriteExt
     pub async fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
-        let addrs = addr.to_socket_addrs().await?;
+        let addrs = to_socket_addrs(addr).await?;
 
         let mut last_err = None;
 
diff --git a/tokio/src/net/udp/socket.rs b/tokio/src/net/udp/socket.rs
index d0dece3e..1b943184 100644
--- a/tokio/src/net/udp/socket.rs
+++ b/tokio/src/net/udp/socket.rs
@@ -1,5 +1,5 @@
 use crate::io::PollEvented;
-use crate::net::ToSocketAddrs;
+use crate::net::{to_socket_addrs, ToSocketAddrs};
 
 use std::convert::TryFrom;
 use std::fmt;
@@ -17,7 +17,7 @@ impl UdpSocket {
     /// This function will create a new UDP socket and attempt to bind it to
     /// the `addr` provided.
     pub async fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
-        let addrs = addr.to_socket_addrs().await?;
+        let addrs = to_socket_addrs(addr).await?;
         let mut last_err = None;
 
         for addr in addrs {
@@ -76,7 +76,7 @@ impl UdpSocket {
     /// limiting packets that are read via recv from the address specified in
     /// `addr`.
     pub async fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
-        let addrs = addr.to_socket_addrs().await?;
+        let addrs = to_socket_addrs(addr).await?;
         let mut last_err = None;
 
         for addr in addrs {
@@ -145,7 +145,7 @@ impl UdpSocket {
     /// The future will resolve to an error if the IP version of the socket does
     /// not match that of `target`.
     pub async fn send_to<A: ToSocketAddrs>(&self, buf: &[u8], target: A) -> io::Result<usize> {
-        let mut addrs = target.to_socket_addrs().await?;
+        let mut addrs = to_socket_addrs(target).await?;
 
         match addrs.next() {
             Some(target) => self.send_to_addr(buf, &target).await,