Rollup merge of rust-lang#58034 - faern:stabilize-time-checked-add, r=alexcrichton

Stabilize the time_checked_add feature

Closes rust-lang#55940

Stabilizes `checked_add` and `checked_sub` on `Instant` and `SystemTime`.

Author: Centril

src/libstd/time.rs

@@ -245,17 +245,17 @@ impl Instant {
     /// Returns `Some(t)` where `t` is the time `self + duration` if `t` can be represented as
     /// `Instant` (which means it's inside the bounds of the underlying data structure), `None`
     /// otherwise.
-    #[unstable(feature = "time_checked_add", issue = "55940")]
+    #[stable(feature = "time_checked_add", since = "1.34.0")]
     pub fn checked_add(&self, duration: Duration) -> Option<Instant> {
-        self.0.checked_add_duration(&duration).map(|t| Instant(t))
+        self.0.checked_add_duration(&duration).map(Instant)
     }
 
     /// Returns `Some(t)` where `t` is the time `self - duration` if `t` can be represented as
     /// `Instant` (which means it's inside the bounds of the underlying data structure), `None`
     /// otherwise.
-    #[unstable(feature = "time_checked_add", issue = "55940")]
+    #[stable(feature = "time_checked_add", since = "1.34.0")]
     pub fn checked_sub(&self, duration: Duration) -> Option<Instant> {
-        self.0.checked_sub_duration(&duration).map(|t| Instant(t))
+        self.0.checked_sub_duration(&duration).map(Instant)
     }
 }
 
@@ -418,17 +418,17 @@ impl SystemTime {
     /// Returns `Some(t)` where `t` is the time `self + duration` if `t` can be represented as
     /// `SystemTime` (which means it's inside the bounds of the underlying data structure), `None`
     /// otherwise.
-    #[unstable(feature = "time_checked_add", issue = "55940")]
+    #[stable(feature = "time_checked_add", since = "1.34.0")]
     pub fn checked_add(&self, duration: Duration) -> Option<SystemTime> {
-        self.0.checked_add_duration(&duration).map(|t| SystemTime(t))
+        self.0.checked_add_duration(&duration).map(SystemTime)
     }
 
     /// Returns `Some(t)` where `t` is the time `self - duration` if `t` can be represented as
     /// `SystemTime` (which means it's inside the bounds of the underlying data structure), `None`
     /// otherwise.
-    #[unstable(feature = "time_checked_add", issue = "55940")]
+    #[stable(feature = "time_checked_add", since = "1.34.0")]
     pub fn checked_sub(&self, duration: Duration) -> Option<SystemTime> {
-        self.0.checked_sub_duration(&duration).map(|t| SystemTime(t))
+        self.0.checked_sub_duration(&duration).map(SystemTime)
     }
 }