Change:
(self.segments()[0] & 0xfe00) == 0xfc00 } <del> /// Returns [`true`] if the address is unicast and link-local (fe80::/10). </del> <ins> /// Returns [`true`] if the address is a unicast link-local address (`fe80::/64`). </ins> /// <del> /// This property is defined in [IETF RFC 4291]. </del> <ins> /// A common mis-conception is to think that "unicast link-local addresses start with /// `fe80::`", but the [IETF RFC 4291] actually defines a stricter format for these addresses: /// /// ```no_rust /// |   10     | /// |  bits    |         54 bits         |          64 bits           | /// +----------+-------------------------+----------------------------+ /// |1111111010|           0             |       interface ID         | /// +----------+-------------------------+----------------------------+ /// ``` /// /// This method validates the format defined in the RFC and won't recognize the following /// addresses such as `fe80:0:0:1::` or `fe81::` as unicast link-local addresses for example. /// If you need a less strict validation use [`is_unicast_link_local()`] instead. /// /// # Examples /// /// ``` /// #![feature(ip)] /// /// use std::net::Ipv6Addr; /// /// fn main() { ///     let ip = Ipv6Addr::new(0xfe80, 0, 0, 0, 0, 0, 0, 0); ///     assert!(ip.is_unicast_link_local_strict()); /// ///     let ip = Ipv6Addr::new(0xfe80, 0, 0, 0, 0xffff, 0xffff, 0xffff, 0xffff); ///     assert!(ip.is_unicast_link_local_strict()); /// ///     let ip = Ipv6Addr::new(0xfe80, 0, 0, 1, 0, 0, 0, 0); ///     assert!(!ip.is_unicast_link_local_strict()); ///     assert!(ip.is_unicast_link_local()); /// ///     let ip = Ipv6Addr::new(0xfe81, 0, 0, 0, 0, 0, 0, 0); ///     assert!(!ip.is_unicast_link_local_strict()); ///     assert!(ip.is_unicast_link_local()); /// } /// ``` /// /// # See also /// /// - [IETF RFC 4291 section 2.5.6] /// - [RFC 4291 errata 4406] /// - [`is_unicast_link_local()`] </ins> /// /// [IETF RFC 4291]: https://tools.ietf.org/html/rfc4291 <ins> /// [IETF RFC 4291 section 2.5.6]: https://tools.ietf.org/html/rfc4291#section-2.5.6 </ins> /// [`true`]: ../../std/primitive.bool.html <ins> /// [RFC 4291 errata 4406]: https://www.rfc-editor.org/errata/eid4406 /// [`is_unicast_link_local()`]: ../../std/net/struct.Ipv6Addr.html#method.is_unicast_link_local /// pub fn is_unicast_link_local_strict(&self) -> bool { (self.segments()[0] & 0xffff) == 0xfe80 && (self.segments()[1] & 0xffff) == 0 && (self.segments()[2] & 0xffff) == 0 && (self.segments()[3] & 0xffff) == 0 } /// Returns [`true`] if the address is a unicast link-local address (`fe80::/10`). /// /// This method returns [`true`] for addresses in the range reserved by [RFC 4291 section 2.4], /// i.e. addresses with the following format: /// /// ```no_rust /// |   10     | /// |  bits    |         54 bits         |          64 bits           | /// +----------+-------------------------+----------------------------+ /// |1111111010|    arbitratry value     |       interface ID         | /// +----------+-------------------------+----------------------------+ /// ``` /// /// As a result, this method consider addresses such as `fe80:0:0:1::` or `fe81::` to be /// unicast link-local addresses, whereas [`is_unicast_link_local_strict()`] does not. If you /// need a strict validation fully compliant with the RFC, use /// [`is_unicast_link_local_strict()`]. </ins> /// /// # Examples ///

Discussion:
This code should be correct, because according to document, all address in are not global reachable. But it panic on assertion failed in latest nightly (2019-01-11) (see )
Relevant thread:
Sorry, fixed