Include scope id in SocketAddrV6::Display

library/std/src/net/addr.rs

@@ -623,19 +623,27 @@ impl fmt::Display for SocketAddrV6 {
         // Fast path: if there's no alignment stuff, write to the output
         // buffer directly
         if f.precision().is_none() && f.width().is_none() {
-            write!(f, "[{}]:{}", self.ip(), self.port())
+            match self.scope_id() {
+                0 => write!(f, "[{}]:{}", self.ip(), self.port()),
+                scope_id => write!(f, "[{}%{}]:{}", self.ip(), scope_id, self.port()),
+            }
         } else {
             const IPV6_SOCKET_BUF_LEN: usize = (4 * 8)  // The address
             + 7  // The colon separators
             + 2  // The brackets
+            + 1 + 10 // The scope id
             + 1 + 5; // The port
 
             let mut buf = [0; IPV6_SOCKET_BUF_LEN];
             let mut buf_slice = &mut buf[..];
 
+            match self.scope_id() {
+                0 => write!(buf_slice, "[{}]:{}", self.ip(), self.port()),
+                scope_id => write!(buf_slice, "[{}%{}]:{}", self.ip(), scope_id, self.port()),
+            }
             // Unwrap is fine because writing to a sufficiently-sized
             // buffer is infallible
-            write!(buf_slice, "[{}]:{}", self.ip(), self.port()).unwrap();
+            .unwrap();
             let len = IPV6_SOCKET_BUF_LEN - buf_slice.len();
 
             // This unsafe is OK because we know what is being written to the buffer

library/std/src/net/addr/tests.rs

@@ -178,13 +178,21 @@ fn socket_v4_to_str() {
 
 #[test]
 fn socket_v6_to_str() {
-    let socket: SocketAddrV6 = "[2a02:6b8:0:1::1]:53".parse().unwrap();
+    let mut socket = SocketAddrV6::new(Ipv6Addr::new(0x2a02, 0x6b8, 0, 1, 0, 0, 0, 1), 53, 0, 0);
 
     assert_eq!(format!("{}", socket), "[2a02:6b8:0:1::1]:53");
     assert_eq!(format!("{:<24}", socket), "[2a02:6b8:0:1::1]:53    ");
     assert_eq!(format!("{:>24}", socket), "    [2a02:6b8:0:1::1]:53");
     assert_eq!(format!("{:^24}", socket), "  [2a02:6b8:0:1::1]:53  ");
     assert_eq!(format!("{:.15}", socket), "[2a02:6b8:0:1::");
+
+    socket.set_scope_id(5);
+
+    assert_eq!(format!("{}", socket), "[2a02:6b8:0:1::1%5]:53");
+    assert_eq!(format!("{:<24}", socket), "[2a02:6b8:0:1::1%5]:53  ");
+    assert_eq!(format!("{:>24}", socket), "  [2a02:6b8:0:1::1%5]:53");
+    assert_eq!(format!("{:^24}", socket), " [2a02:6b8:0:1::1%5]:53 ");
+    assert_eq!(format!("{:.18}", socket), "[2a02:6b8:0:1::1%5");
 }
 
 #[test]