also apply revert to wasip2

Author: RalfJung

library/std/src/sys/pal/wasip2/time.rs

@@ -36,34 +36,23 @@ impl SystemTime {
         SystemTime(Duration::new(now.seconds, now.nanoseconds))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn from_wasi_timestamp(ts: wasi::Timestamp) -> SystemTime {
+    pub fn from_wasi_timestamp(ts: wasi::Timestamp) -> SystemTime {
         SystemTime(Duration::from_nanos(ts))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn to_wasi_timestamp(&self) -> Option<wasi::Timestamp> {
-        // FIXME: const TryInto
-        let ns = self.0.as_nanos();
-        if ns <= u64::MAX as u128 { Some(ns as u64) } else { None }
+    pub fn to_wasi_timestamp(&self) -> Option<wasi::Timestamp> {
+        self.0.as_nanos().try_into().ok()
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
-        // FIXME: ok_or_else with const closures
-        match self.0.checked_sub(other.0) {
-            Some(duration) => Ok(duration),
-            None => Err(other.0 - self.0),
-        }
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        self.0.checked_sub(other.0).ok_or_else(|| other.0 - self.0)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_add(*other)?))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_sub(*other)?))
     }
 }