Recreate ctr-std from latest nightly

2 files changed, 356 insertions, 69 deletions

diff --git a/ctr-std/src/time/duration.rs b/ctr-std/src/time/duration.rs
index 41d675b..cb5bfb9 100644
--- a/ctr-std/src/time/duration.rs
+++ b/ctr-std/src/time/duration.rs
@@ -1,4 +1,4 @@
-// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -8,22 +8,29 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use iter::Sum;
 use ops::{Add, Sub, Mul, Div, AddAssign, SubAssign, MulAssign, DivAssign};
 
 const NANOS_PER_SEC: u32 = 1_000_000_000;
 const NANOS_PER_MILLI: u32 = 1_000_000;
+const NANOS_PER_MICRO: u32 = 1_000;
 const MILLIS_PER_SEC: u64 = 1_000;
+const MICROS_PER_SEC: u64 = 1_000_000;
 
-/// A duration type to represent a span of time, typically used for system
+/// A `Duration` type to represent a span of time, typically used for system
 /// timeouts.
 ///
-/// Each duration is composed of a number of seconds and nanosecond precision.
-/// APIs binding a system timeout will typically round up the nanosecond
-/// precision if the underlying system does not support that level of precision.
+/// Each `Duration` is composed of a whole number of seconds and a fractional part
+/// represented in nanoseconds.  If the underlying system does not support
+/// nanosecond-level precision, APIs binding a system timeout will typically round up
+/// the number of nanoseconds.
 ///
-/// Durations implement many common traits, including `Add`, `Sub`, and other
-/// ops traits. Currently a duration may only be inspected for its number of
-/// seconds and its nanosecond precision.
+/// `Duration`s implement many common traits, including [`Add`], [`Sub`], and other
+/// [`ops`] traits.
+///
+/// [`Add`]: ../../std/ops/trait.Add.html
+/// [`Sub`]: ../../std/ops/trait.Sub.html
+/// [`ops`]: ../../std/ops/index.html
 ///
 /// # Examples
 ///
@@ -46,16 +53,24 @@ pub struct Duration {
 }
 
 impl Duration {
-    /// Creates a new `Duration` from the specified number of seconds and
-    /// additional nanosecond precision.
+    /// Creates a new `Duration` from the specified number of whole seconds and
+    /// additional nanoseconds.
     ///
-    /// If the nanoseconds is greater than 1 billion (the number of nanoseconds
-    /// in a second), then it will carry over into the seconds provided.
+    /// If the number of nanoseconds is greater than 1 billion (the number of
+    /// nanoseconds in a second), then it will carry over into the seconds provided.
     ///
     /// # Panics
     ///
     /// This constructor will panic if the carry from the nanoseconds overflows
     /// the seconds counter.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Duration;
+    ///
+    /// let five_seconds = Duration::new(5, 0);
+    /// ```
     #[stable(feature = "duration", since = "1.3.0")]
     #[inline]
     pub fn new(secs: u64, nanos: u32) -> Duration {
@@ -65,7 +80,18 @@ impl Duration {
         Duration { secs: secs, nanos: nanos }
     }
 
-    /// Creates a new `Duration` from the specified number of seconds.
+    /// Creates a new `Duration` from the specified number of whole seconds.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Duration;
+    ///
+    /// let duration = Duration::from_secs(5);
+    ///
+    /// assert_eq!(5, duration.as_secs());
+    /// assert_eq!(0, duration.subsec_nanos());
+    /// ```
     #[stable(feature = "duration", since = "1.3.0")]
     #[inline]
     pub fn from_secs(secs: u64) -> Duration {
@@ -73,6 +99,17 @@ impl Duration {
     }
 
     /// Creates a new `Duration` from the specified number of milliseconds.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Duration;
+    ///
+    /// let duration = Duration::from_millis(2569);
+    ///
+    /// assert_eq!(2, duration.as_secs());
+    /// assert_eq!(569_000_000, duration.subsec_nanos());
+    /// ```
     #[stable(feature = "duration", since = "1.3.0")]
     #[inline]
     pub fn from_millis(millis: u64) -> Duration {
@@ -81,39 +118,155 @@ impl Duration {
         Duration { secs: secs, nanos: nanos }
     }
 
-    /// Returns the number of whole seconds represented by this duration.
+    /// Creates a new `Duration` from the specified number of microseconds.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(duration_from_micros)]
+    /// use std::time::Duration;
+    ///
+    /// let duration = Duration::from_micros(1_000_002);
+    ///
+    /// assert_eq!(1, duration.as_secs());
+    /// assert_eq!(2000, duration.subsec_nanos());
+    /// ```
+    #[unstable(feature = "duration_from_micros", issue = "44400")]
+    #[inline]
+    pub fn from_micros(micros: u64) -> Duration {
+        let secs = micros / MICROS_PER_SEC;
+        let nanos = ((micros % MICROS_PER_SEC) as u32) * NANOS_PER_MICRO;
+        Duration { secs: secs, nanos: nanos }
+    }
+
+    /// Creates a new `Duration` from the specified number of nanoseconds.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(duration_extras)]
+    /// use std::time::Duration;
+    ///
+    /// let duration = Duration::from_nanos(1_000_000_123);
+    ///
+    /// assert_eq!(1, duration.as_secs());
+    /// assert_eq!(123, duration.subsec_nanos());
+    /// ```
+    #[unstable(feature = "duration_extras", issue = "46507")]
+    #[inline]
+    pub fn from_nanos(nanos: u64) -> Duration {
+        let secs = nanos / (NANOS_PER_SEC as u64);
+        let nanos = (nanos % (NANOS_PER_SEC as u64)) as u32;
+        Duration { secs: secs, nanos: nanos }
+    }
+
+    /// Returns the number of _whole_ seconds contained by this `Duration`.
+    ///
+    /// The returned value does not include the fractional (nanosecond) part of the
+    /// duration, which can be obtained using [`subsec_nanos`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Duration;
+    ///
+    /// let duration = Duration::new(5, 730023852);
+    /// assert_eq!(duration.as_secs(), 5);
+    /// ```
+    ///
+    /// To determine the total number of seconds represented by the `Duration`,
+    /// use `as_secs` in combination with [`subsec_nanos`]:
+    ///
+    /// ```
+    /// use std::time::Duration;
     ///
-    /// The extra precision represented by this duration is ignored (i.e. extra
-    /// nanoseconds are not represented in the returned value).
+    /// let duration = Duration::new(5, 730023852);
+    ///
+    /// assert_eq!(5.730023852,
+    ///            duration.as_secs() as f64
+    ///            + duration.subsec_nanos() as f64 * 1e-9);
+    /// ```
+    ///
+    /// [`subsec_nanos`]: #method.subsec_nanos
     #[stable(feature = "duration", since = "1.3.0")]
     #[inline]
     pub fn as_secs(&self) -> u64 { self.secs }
 
-    /// Returns the nanosecond precision represented by this duration.
+    /// Returns the fractional part of this `Duration`, in milliseconds.
+    ///
+    /// This method does **not** return the length of the duration when
+    /// represented by milliseconds. The returned number always represents a
+    /// fractional portion of a second (i.e. it is less than one thousand).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(duration_extras)]
+    /// use std::time::Duration;
+    ///
+    /// let duration = Duration::from_millis(5432);
+    /// assert_eq!(duration.as_secs(), 5);
+    /// assert_eq!(duration.subsec_millis(), 432);
+    /// ```
+    #[unstable(feature = "duration_extras", issue = "46507")]
+    #[inline]
+    pub fn subsec_millis(&self) -> u32 { self.nanos / NANOS_PER_MILLI }
+
+    /// Returns the fractional part of this `Duration`, in microseconds.
+    ///
+    /// This method does **not** return the length of the duration when
+    /// represented by microseconds. The returned number always represents a
+    /// fractional portion of a second (i.e. it is less than one million).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(duration_extras, duration_from_micros)]
+    /// use std::time::Duration;
+    ///
+    /// let duration = Duration::from_micros(1_234_567);
+    /// assert_eq!(duration.as_secs(), 1);
+    /// assert_eq!(duration.subsec_micros(), 234_567);
+    /// ```
+    #[unstable(feature = "duration_extras", issue = "46507")]
+    #[inline]
+    pub fn subsec_micros(&self) -> u32 { self.nanos / NANOS_PER_MICRO }
+
+    /// Returns the fractional part of this `Duration`, in nanoseconds.
     ///
     /// This method does **not** return the length of the duration when
     /// represented by nanoseconds. The returned number always represents a
     /// fractional portion of a second (i.e. it is less than one billion).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Duration;
+    ///
+    /// let duration = Duration::from_millis(5010);
+    /// assert_eq!(duration.as_secs(), 5);
+    /// assert_eq!(duration.subsec_nanos(), 10_000_000);
+    /// ```
     #[stable(feature = "duration", since = "1.3.0")]
     #[inline]
     pub fn subsec_nanos(&self) -> u32 { self.nanos }
 
-    /// Checked duration addition. Computes `self + other`, returning `None`
+    /// Checked `Duration` addition. Computes `self + other`, returning [`None`]
     /// if overflow occurred.
     ///
+    /// [`None`]: ../../std/option/enum.Option.html#variant.None
+    ///
     /// # Examples
     ///
     /// Basic usage:
     ///
     /// ```
-    /// #![feature(duration_checked_ops)]
-    ///
     /// use std::time::Duration;
     ///
     /// assert_eq!(Duration::new(0, 0).checked_add(Duration::new(0, 1)), Some(Duration::new(0, 1)));
     /// assert_eq!(Duration::new(1, 0).checked_add(Duration::new(std::u64::MAX, 0)), None);
     /// ```
-    #[unstable(feature = "duration_checked_ops", issue = "35774")]
+    #[stable(feature = "duration_checked_ops", since = "1.16.0")]
     #[inline]
     pub fn checked_add(self, rhs: Duration) -> Option<Duration> {
         if let Some(mut secs) = self.secs.checked_add(rhs.secs) {
@@ -128,30 +281,30 @@ impl Duration {
             }
             debug_assert!(nanos < NANOS_PER_SEC);
             Some(Duration {
-                secs: secs,
-                nanos: nanos,
+                secs,
+                nanos,
             })
         } else {
             None
         }
     }
 
-    /// Checked duration subtraction. Computes `self + other`, returning `None`
-    /// if the result would be negative or if underflow occurred.
+    /// Checked `Duration` subtraction. Computes `self - other`, returning [`None`]
+    /// if the result would be negative or if overflow occurred.
+    ///
+    /// [`None`]: ../../std/option/enum.Option.html#variant.None
     ///
     /// # Examples
     ///
     /// Basic usage:
     ///
     /// ```
-    /// #![feature(duration_checked_ops)]
-    ///
     /// use std::time::Duration;
     ///
     /// assert_eq!(Duration::new(0, 1).checked_sub(Duration::new(0, 0)), Some(Duration::new(0, 1)));
     /// assert_eq!(Duration::new(0, 0).checked_sub(Duration::new(0, 1)), None);
     /// ```
-    #[unstable(feature = "duration_checked_ops", issue = "35774")]
+    #[stable(feature = "duration_checked_ops", since = "1.16.0")]
     #[inline]
     pub fn checked_sub(self, rhs: Duration) -> Option<Duration> {
         if let Some(mut secs) = self.secs.checked_sub(rhs.secs) {
@@ -172,22 +325,22 @@ impl Duration {
         }
     }
 
-    /// Checked duration multiplication. Computes `self * other`, returning
-    /// `None` if underflow or overflow occurred.
+    /// Checked `Duration` multiplication. Computes `self * other`, returning
+    /// [`None`] if overflow occurred.
+    ///
+    /// [`None`]: ../../std/option/enum.Option.html#variant.None
     ///
     /// # Examples
     ///
     /// Basic usage:
     ///
     /// ```
-    /// #![feature(duration_checked_ops)]
-    ///
     /// use std::time::Duration;
     ///
     /// assert_eq!(Duration::new(0, 500_000_001).checked_mul(2), Some(Duration::new(1, 2)));
     /// assert_eq!(Duration::new(std::u64::MAX - 1, 0).checked_mul(2), None);
     /// ```
-    #[unstable(feature = "duration_checked_ops", issue = "35774")]
+    #[stable(feature = "duration_checked_ops", since = "1.16.0")]
     #[inline]
     pub fn checked_mul(self, rhs: u32) -> Option<Duration> {
         // Multiply nanoseconds as u64, because it cannot overflow that way.
@@ -199,31 +352,31 @@ impl Duration {
             .and_then(|s| s.checked_add(extra_secs)) {
             debug_assert!(nanos < NANOS_PER_SEC);
             Some(Duration {
-                secs: secs,
-                nanos: nanos,
+                secs,
+                nanos,
             })
         } else {
             None
         }
     }
 
-    /// Checked duration division. Computes `self / other`, returning `None`
-    /// if `other == 0` or the operation results in underflow or overflow.
+    /// Checked `Duration` division. Computes `self / other`, returning [`None`]
+    /// if `other == 0`.
+    ///
+    /// [`None`]: ../../std/option/enum.Option.html#variant.None
     ///
     /// # Examples
     ///
     /// Basic usage:
     ///
     /// ```
-    /// #![feature(duration_checked_ops)]
-    ///
     /// use std::time::Duration;
     ///
     /// assert_eq!(Duration::new(2, 0).checked_div(2), Some(Duration::new(1, 0)));
     /// assert_eq!(Duration::new(1, 0).checked_div(2), Some(Duration::new(0, 500_000_000)));
     /// assert_eq!(Duration::new(2, 0).checked_div(0), None);
     /// ```
-    #[unstable(feature = "duration_checked_ops", issue = "35774")]
+    #[stable(feature = "duration_checked_ops", since = "1.16.0")]
     #[inline]
     pub fn checked_div(self, rhs: u32) -> Option<Duration> {
         if rhs != 0 {
@@ -303,6 +456,20 @@ impl DivAssign<u32> for Duration {
     }
 }
 
+#[stable(feature = "duration_sum", since = "1.16.0")]
+impl Sum for Duration {
+    fn sum<I: Iterator<Item=Duration>>(iter: I) -> Duration {
+        iter.fold(Duration::new(0, 0), |a, b| a + b)
+    }
+}
+
+#[stable(feature = "duration_sum", since = "1.16.0")]
+impl<'a> Sum<&'a Duration> for Duration {
+    fn sum<I: Iterator<Item=&'a Duration>>(iter: I) -> Duration {
+        iter.fold(Duration::new(0, 0), |a, b| a + *b)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::Duration;
diff --git a/ctr-std/src/time/mod.rs b/ctr-std/src/time/mod.rs
index 6854f1e..6ce3b3e 100644
--- a/ctr-std/src/time/mod.rs
+++ b/ctr-std/src/time/mod.rs
@@ -33,10 +33,10 @@ pub use self::duration::Duration;
 
 mod duration;
 
-/// A measurement of a monotonically increasing clock.
-///  Opaque and useful only with `Duration`.
+/// A measurement of a monotonically nondecreasing clock.
+/// Opaque and useful only with `Duration`.
 ///
-/// Instants are always guaranteed to be greater than any previously measured
+/// Instants are always guaranteed to be no less than any previously measured
 /// instant when created, and are often useful for tasks such as measuring
 /// benchmarks or timing how long an operation takes.
 ///
@@ -66,14 +66,14 @@ mod duration;
 ///    println!("{}", now.elapsed().as_secs());
 /// }
 /// ```
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[stable(feature = "time2", since = "1.8.0")]
 pub struct Instant(time::Instant);
 
 /// A measurement of the system clock, useful for talking to
 /// external entities like the file system or other processes.
 ///
-/// Distinct from the `Instant` type, this time measurement **is not
+/// Distinct from the [`Instant`] type, this time measurement **is not
 /// monotonic**. This means that you can save a file to the file system, then
 /// save another file to the file system, **and the second file has a
 /// `SystemTime` measurement earlier than the first**. In other words, an
@@ -81,15 +81,20 @@ pub struct Instant(time::Instant);
 /// earlier `SystemTime`!
 ///
 /// Consequently, comparing two `SystemTime` instances to learn about the
-/// duration between them returns a `Result` instead of an infallible `Duration`
+/// duration between them returns a [`Result`] instead of an infallible [`Duration`]
 /// to indicate that this sort of time drift may happen and needs to be handled.
 ///
-/// Although a `SystemTime` cannot be directly inspected, the `UNIX_EPOCH`
+/// Although a `SystemTime` cannot be directly inspected, the [`UNIX_EPOCH`]
 /// constant is provided in this module as an anchor in time to learn
 /// information about a `SystemTime`. By calculating the duration from this
 /// fixed point in time, a `SystemTime` can be converted to a human-readable time,
 /// or perhaps some other string representation.
 ///
+/// [`Instant`]: ../../std/time/struct.Instant.html
+/// [`Result`]: ../../std/result/enum.Result.html
+/// [`Duration`]: ../../std/time/struct.Duration.html
+/// [`UNIX_EPOCH`]: ../../std/time/constant.UNIX_EPOCH.html
+///
 /// Example:
 ///
 /// ```no_run
@@ -107,24 +112,48 @@ pub struct Instant(time::Instant);
 ///            println!("{}", elapsed.as_secs());
 ///        }
 ///        Err(e) => {
-///            // an error occured!
+///            // an error occurred!
 ///            println!("Error: {:?}", e);
 ///        }
 ///    }
 /// }
 /// ```
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[stable(feature = "time2", since = "1.8.0")]
 pub struct SystemTime(time::SystemTime);
 
-/// An error returned from the `duration_since` method on `SystemTime`,
-/// used to learn how far in the opposite direction a system time lies.
+/// An error returned from the `duration_since` and `elapsed` methods on
+/// `SystemTime`, used to learn how far in the opposite direction a system time
+/// lies.
+///
+/// # Examples
+///
+/// ```no_run
+/// use std::thread::sleep;
+/// use std::time::{Duration, SystemTime};
+///
+/// let sys_time = SystemTime::now();
+/// sleep(Duration::from_secs(1));
+/// let new_sys_time = SystemTime::now();
+/// match sys_time.duration_since(new_sys_time) {
+///     Ok(_) => {}
+///     Err(e) => println!("SystemTimeError difference: {:?}", e.duration()),
+/// }
+/// ```
 #[derive(Clone, Debug)]
 #[stable(feature = "time2", since = "1.8.0")]
 pub struct SystemTimeError(Duration);
 
 impl Instant {
     /// Returns an instant corresponding to "now".
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Instant;
+    ///
+    /// let now = Instant::now();
+    /// ```
     #[stable(feature = "time2", since = "1.8.0")]
     pub fn now() -> Instant {
         Instant(time::Instant::now())
@@ -134,10 +163,19 @@ impl Instant {
     ///
     /// # Panics
     ///
-    /// This function will panic if `earlier` is later than `self`, which should
-    /// only be possible if `earlier` was created after `self`. Because
-    /// `Instant` is monotonic, the only time that this should happen should be
-    /// a bug.
+    /// This function will panic if `earlier` is later than `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::time::{Duration, Instant};
+    /// use std::thread::sleep;
+    ///
+    /// let now = Instant::now();
+    /// sleep(Duration::new(1, 0));
+    /// let new_now = Instant::now();
+    /// println!("{:?}", new_now.duration_since(now));
+    /// ```
     #[stable(feature = "time2", since = "1.8.0")]
     pub fn duration_since(&self, earlier: Instant) -> Duration {
         self.0.sub_instant(&earlier.0)
@@ -218,6 +256,14 @@ impl fmt::Debug for Instant {
 
 impl SystemTime {
     /// Returns the system time corresponding to "now".
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::SystemTime;
+    ///
+    /// let sys_time = SystemTime::now();
+    /// ```
     #[stable(feature = "time2", since = "1.8.0")]
     pub fn now() -> SystemTime {
         SystemTime(time::SystemTime::now())
@@ -229,11 +275,26 @@ impl SystemTime {
     /// guaranteed to always be before later measurements (due to anomalies such
     /// as the system clock being adjusted either forwards or backwards).
     ///
-    /// If successful, `Ok(Duration)` is returned where the duration represents
+    /// If successful, [`Ok`]`(`[`Duration`]`)` is returned where the duration represents
     /// the amount of time elapsed from the specified measurement to this one.
     ///
-    /// Returns an `Err` if `earlier` is later than `self`, and the error
+    /// Returns an [`Err`] if `earlier` is later than `self`, and the error
     /// contains how far from `self` the time is.
+    ///
+    /// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
+    /// [`Duration`]: ../../std/time/struct.Duration.html
+    /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::SystemTime;
+    ///
+    /// let sys_time = SystemTime::now();
+    /// let difference = sys_time.duration_since(sys_time)
+    ///                          .expect("SystemTime::duration_since failed");
+    /// println!("{:?}", difference);
+    /// ```
     #[stable(feature = "time2", since = "1.8.0")]
     pub fn duration_since(&self, earlier: SystemTime)
                           -> Result<Duration, SystemTimeError> {
@@ -244,12 +305,28 @@ impl SystemTime {
     ///
     /// This function may fail as the underlying system clock is susceptible to
     /// drift and updates (e.g. the system clock could go backwards), so this
-    /// function may not always succeed. If successful, `Ok(duration)` is
+    /// function may not always succeed. If successful, [`Ok`]`(`[`Duration`]`)` is
     /// returned where the duration represents the amount of time elapsed from
     /// this time measurement to the current time.
     ///
-    /// Returns an `Err` if `self` is later than the current system time, and
+    /// Returns an [`Err`] if `self` is later than the current system time, and
     /// the error contains how far from the current system time `self` is.
+    ///
+    /// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
+    /// [`Duration`]: ../../std/time/struct.Duration.html
+    /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::thread::sleep;
+    /// use std::time::{Duration, SystemTime};
+    ///
+    /// let sys_time = SystemTime::now();
+    /// let one_sec = Duration::from_secs(1);
+    /// sleep(one_sec);
+    /// assert!(sys_time.elapsed().unwrap() >= one_sec);
+    /// ```
     #[stable(feature = "time2", since = "1.8.0")]
     pub fn elapsed(&self) -> Result<Duration, SystemTimeError> {
         SystemTime::now().duration_since(*self)
@@ -300,9 +377,22 @@ impl fmt::Debug for SystemTime {
 ///
 /// This constant is defined to be "1970-01-01 00:00:00 UTC" on all systems with
 /// respect to the system clock. Using `duration_since` on an existing
-/// `SystemTime` instance can tell how far away from this point in time a
+/// [`SystemTime`] instance can tell how far away from this point in time a
 /// measurement lies, and using `UNIX_EPOCH + duration` can be used to create a
-/// `SystemTime` instance to represent another fixed point in time.
+/// [`SystemTime`] instance to represent another fixed point in time.
+///
+/// [`SystemTime`]: ../../std/time/struct.SystemTime.html
+///
+/// # Examples
+///
+/// ```no_run
+/// use std::time::{SystemTime, UNIX_EPOCH};
+///
+/// match SystemTime::now().duration_since(UNIX_EPOCH) {
+///     Ok(n) => println!("1970-01-01 00:00:00 UTC was {} seconds ago!", n.as_secs()),
+///     Err(_) => panic!("SystemTime before UNIX EPOCH!"),
+/// }
+/// ```
 #[stable(feature = "time2", since = "1.8.0")]
 pub const UNIX_EPOCH: SystemTime = SystemTime(time::UNIX_EPOCH);
 
@@ -310,9 +400,28 @@ impl SystemTimeError {
     /// Returns the positive duration which represents how far forward the
     /// second system time was from the first.
     ///
-    /// A `SystemTimeError` is returned from the `duration_since`
-    /// operation whenever the second system time represents a point later
+    /// A `SystemTimeError` is returned from the [`duration_since`] and [`elapsed`]
+    /// methods of [`SystemTime`] whenever the second system time represents a point later
     /// in time than the `self` of the method call.
+    ///
+    /// [`duration_since`]: ../../std/time/struct.SystemTime.html#method.duration_since
+    /// [`elapsed`]: ../../std/time/struct.SystemTime.html#method.elapsed
+    /// [`SystemTime`]: ../../std/time/struct.SystemTime.html
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::thread::sleep;
+    /// use std::time::{Duration, SystemTime};
+    ///
+    /// let sys_time = SystemTime::now();
+    /// sleep(Duration::from_secs(1));
+    /// let new_sys_time = SystemTime::now();
+    /// match sys_time.duration_since(new_sys_time) {
+    ///     Ok(_) => {}
+    ///     Err(e) => println!("SystemTimeError difference: {:?}", e.duration()),
+    /// }
+    /// ```
     #[stable(feature = "time2", since = "1.8.0")]
     pub fn duration(&self) -> Duration {
         self.0
@@ -400,7 +509,7 @@ mod tests {
                 let dur = dur.duration();
                 assert!(a > b);
                 assert_almost_eq!(b + dur, a);
-                assert_almost_eq!(b - dur, a);
+                assert_almost_eq!(a - dur, b);
             }
         }
 
@@ -411,9 +520,12 @@ mod tests {
 
         assert_almost_eq!(a - second + second, a);
 
-        let eighty_years = second * 60 * 60 * 24 * 365 * 80;
-        assert_almost_eq!(a - eighty_years + eighty_years, a);
-        assert_almost_eq!(a - (eighty_years * 10) + (eighty_years * 10), a);
+        // A difference of 80 and 800 years cannot fit inside a 32-bit time_t
+        if !(cfg!(unix) && ::mem::size_of::<::libc::time_t>() <= 4) {
+            let eighty_years = second * 60 * 60 * 24 * 365 * 80;
+            assert_almost_eq!(a - eighty_years + eighty_years, a);
+            assert_almost_eq!(a - (eighty_years * 10) + (eighty_years * 10), a);
+        }
 
         let one_second_from_epoch = UNIX_EPOCH + Duration::new(1, 0);
         let one_second_from_epoch2 = UNIX_EPOCH + Duration::new(0, 500_000_000)
@@ -435,9 +547,17 @@ mod tests {
         assert!(b > a);
         assert_eq!(b - a, Duration::new(1, 0));
 
-        // let's assume that we're all running computers later than 2000
         let thirty_years = Duration::new(1, 0) * 60 * 60 * 24 * 365 * 30;
-        assert!(a > thirty_years);
+
+        // Right now for CI this test is run in an emulator, and apparently the
+        // aarch64 emulator's sense of time is that we're still living in the
+        // 70s.
+        //
+        // Otherwise let's assume that we're all running computers later than
+        // 2000.
+        if !cfg!(target_arch = "aarch64") {
+            assert!(a > thirty_years);
+        }
 
         // let's assume that we're all running computers earlier than 2090.
         // Should give us ~70 years to fix this!