Rollup merge of #68640 - LeSeulArtichaut:doc-from-ip, r=steveklabnik

Document remaining undocumented `From` implementations for IPs

Some `From` implementations were missing documentation. I added examples, I tried to be as close to existing examples as possible.

Related to #51430 (cc @skade)

r? @steveklabnik

Author: Dylan-DPC

src/libstd/net/ip.rs

@@ -813,13 +813,41 @@ impl fmt::Display for IpAddr {
 
 #[stable(feature = "ip_from_ip", since = "1.16.0")]
 impl From<Ipv4Addr> for IpAddr {
+    /// Copies this address to a new `IpAddr::V4`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::{IpAddr, Ipv4Addr};
+    ///
+    /// let addr = Ipv4Addr::new(127, 0, 0, 1);
+    ///
+    /// assert_eq!(
+    ///     IpAddr::V4(addr),
+    ///     IpAddr::from(addr)
+    /// )
+    /// ```
     fn from(ipv4: Ipv4Addr) -> IpAddr {
         IpAddr::V4(ipv4)
     }
 }
 
 #[stable(feature = "ip_from_ip", since = "1.16.0")]
 impl From<Ipv6Addr> for IpAddr {
+    /// Copies this address to a new `IpAddr::V6`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::{IpAddr, Ipv6Addr};
+    ///
+    /// let addr = Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc00a, 0x2ff);
+    ///
+    /// assert_eq!(
+    ///     IpAddr::V6(addr),
+    ///     IpAddr::from(addr)
+    /// );
+    /// ```
     fn from(ipv6: Ipv6Addr) -> IpAddr {
         IpAddr::V6(ipv6)
     }
@@ -975,6 +1003,8 @@ impl From<u32> for Ipv4Addr {
 
 #[stable(feature = "from_slice_v4", since = "1.9.0")]
 impl From<[u8; 4]> for Ipv4Addr {
+    /// Creates an `Ipv4Addr` from a four element byte array.
+    ///
     /// # Examples
     ///
     /// ```
@@ -1734,6 +1764,27 @@ impl From<u128> for Ipv6Addr {
 
 #[stable(feature = "ipv6_from_octets", since = "1.9.0")]
 impl From<[u8; 16]> for Ipv6Addr {
+    /// Creates an `Ipv6Addr` from a sixteen element byte array.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::Ipv6Addr;
+    ///
+    /// let addr = Ipv6Addr::from([
+    ///     25u8, 24u8, 23u8, 22u8, 21u8, 20u8, 19u8, 18u8,
+    ///     17u8, 16u8, 15u8, 14u8, 13u8, 12u8, 11u8, 10u8,
+    /// ]);
+    /// assert_eq!(
+    ///     Ipv6Addr::new(
+    ///         0x1918, 0x1716,
+    ///         0x1514, 0x1312,
+    ///         0x1110, 0x0f0e,
+    ///         0x0d0c, 0x0b0a
+    ///     ),
+    ///     addr
+    /// );
+    /// ```
     fn from(octets: [u8; 16]) -> Ipv6Addr {
         let inner = c::in6_addr { s6_addr: octets };
         Ipv6Addr::from_inner(inner)
@@ -1742,6 +1793,27 @@ impl From<[u8; 16]> for Ipv6Addr {
 
 #[stable(feature = "ipv6_from_segments", since = "1.16.0")]
 impl From<[u16; 8]> for Ipv6Addr {
+    /// Creates an `Ipv6Addr` from an eight element 16-bit array.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::Ipv6Addr;
+    ///
+    /// let addr = Ipv6Addr::from([
+    ///     525u16, 524u16, 523u16, 522u16,
+    ///     521u16, 520u16, 519u16, 518u16,
+    /// ]);
+    /// assert_eq!(
+    ///     Ipv6Addr::new(
+    ///         0x20d, 0x20c,
+    ///         0x20b, 0x20a,
+    ///         0x209, 0x208,
+    ///         0x207, 0x206
+    ///     ),
+    ///     addr
+    /// );
+    /// ```
     fn from(segments: [u16; 8]) -> Ipv6Addr {
         let [a, b, c, d, e, f, g, h] = segments;
         Ipv6Addr::new(a, b, c, d, e, f, g, h)