Make methods on NaiveDateTime const where possible

src/naive/datetime/mod.rs

@@ -20,7 +20,9 @@ use crate::format::{parse, parse_and_remainder, ParseError, ParseResult, Parsed,
 use crate::format::{Fixed, Item, Numeric, Pad};
 use crate::naive::{Days, IsoWeek, NaiveDate, NaiveTime};
 use crate::offset::Utc;
-use crate::{DateTime, Datelike, LocalResult, Months, TimeZone, Timelike, Weekday};
+use crate::{
+    expect, try_opt, DateTime, Datelike, LocalResult, Months, TimeZone, Timelike, Weekday,
+};
 
 #[cfg(feature = "rustc-serialize")]
 pub(super) mod rustc_serialize;
@@ -122,9 +124,9 @@ impl NaiveDateTime {
     #[deprecated(since = "0.4.23", note = "use `from_timestamp_opt()` instead")]
     #[inline]
     #[must_use]
-    pub fn from_timestamp(secs: i64, nsecs: u32) -> NaiveDateTime {
+    pub const fn from_timestamp(secs: i64, nsecs: u32) -> NaiveDateTime {
         let datetime = NaiveDateTime::from_timestamp_opt(secs, nsecs);
-        datetime.expect("invalid or out-of-range datetime")
+        expect!(datetime, "invalid or out-of-range datetime")
     }
 
     /// Creates a new [NaiveDateTime] from milliseconds since the UNIX epoch.
@@ -153,7 +155,7 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn from_timestamp_millis(millis: i64) -> Option<NaiveDateTime> {
+    pub const fn from_timestamp_millis(millis: i64) -> Option<NaiveDateTime> {
         let secs = millis.div_euclid(1000);
         let nsecs = millis.rem_euclid(1000) as u32 * 1_000_000;
         NaiveDateTime::from_timestamp_opt(secs, nsecs)
@@ -185,7 +187,7 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn from_timestamp_micros(micros: i64) -> Option<NaiveDateTime> {
+    pub const fn from_timestamp_micros(micros: i64) -> Option<NaiveDateTime> {
         let secs = micros.div_euclid(1_000_000);
         let nsecs = micros.rem_euclid(1_000_000) as u32 * 1000;
         NaiveDateTime::from_timestamp_opt(secs, nsecs)
@@ -222,13 +224,14 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn from_timestamp_opt(secs: i64, nsecs: u32) -> Option<NaiveDateTime> {
+    pub const fn from_timestamp_opt(secs: i64, nsecs: u32) -> Option<NaiveDateTime> {
         let days = secs.div_euclid(86_400);
         let secs = secs.rem_euclid(86_400);
-        let date = i32::try_from(days)
-            .ok()
-            .and_then(|days| days.checked_add(719_163))
-            .and_then(NaiveDate::from_num_days_from_ce_opt);
+        if days < i32::MIN as i64 || days > i32::MAX as i64 {
+            return None;
+        }
+        let date =
+            NaiveDate::from_num_days_from_ce_opt(try_opt!((days as i32).checked_add(719_163)));
         let time = NaiveTime::from_num_seconds_from_midnight_opt(secs as u32, nsecs);
         match (date, time) {
             (Some(date), Some(time)) => Some(NaiveDateTime { date, time }),
@@ -392,10 +395,10 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn timestamp(&self) -> i64 {
+    pub const fn timestamp(&self) -> i64 {
         const UNIX_EPOCH_DAY: i64 = 719_163;
-        let gregorian_day = i64::from(self.date.num_days_from_ce());
-        let seconds_from_midnight = i64::from(self.time.num_seconds_from_midnight());
+        let gregorian_day = self.date.num_days_from_ce() as i64;
+        let seconds_from_midnight = self.time.num_seconds_from_midnight() as i64;
         (gregorian_day - UNIX_EPOCH_DAY) * 86_400 + seconds_from_midnight
     }
 
@@ -420,9 +423,9 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn timestamp_millis(&self) -> i64 {
+    pub const fn timestamp_millis(&self) -> i64 {
         let as_ms = self.timestamp() * 1000;
-        as_ms + i64::from(self.timestamp_subsec_millis())
+        as_ms + self.timestamp_subsec_millis() as i64
     }
 
     /// Returns the number of non-leap *microseconds* since midnight on January 1, 1970.
@@ -443,9 +446,9 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn timestamp_micros(&self) -> i64 {
+    pub const fn timestamp_micros(&self) -> i64 {
         let as_us = self.timestamp() * 1_000_000;
-        as_us + i64::from(self.timestamp_subsec_micros())
+        as_us + self.timestamp_subsec_micros() as i64
     }
 
     /// Returns the number of non-leap *nanoseconds* since midnight on January 1, 1970.
@@ -523,7 +526,7 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn timestamp_subsec_millis(&self) -> u32 {
+    pub const fn timestamp_subsec_millis(&self) -> u32 {
         self.timestamp_subsec_nanos() / 1_000_000
     }
 
@@ -545,7 +548,7 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn timestamp_subsec_micros(&self) -> u32 {
+    pub const fn timestamp_subsec_micros(&self) -> u32 {
         self.timestamp_subsec_nanos() / 1_000
     }
 
@@ -567,7 +570,7 @@ impl NaiveDateTime {
     /// ```
     #[inline]
     #[must_use]
-    pub fn timestamp_subsec_nanos(&self) -> u32 {
+    pub const fn timestamp_subsec_nanos(&self) -> u32 {
         self.time.nanosecond()
     }
 
@@ -647,7 +650,7 @@ impl NaiveDateTime {
             return None;
         }
 
-        let date = self.date.checked_add_signed(OldDuration::seconds(rhs))?;
+        let date = try_opt!(self.date.checked_add_signed(OldDuration::seconds(rhs)));
         Some(NaiveDateTime { date, time })
     }
 
@@ -677,8 +680,8 @@ impl NaiveDateTime {
     /// );
     /// ```
     #[must_use]
-    pub fn checked_add_months(self, rhs: Months) -> Option<NaiveDateTime> {
-        Some(Self { date: self.date.checked_add_months(rhs)?, time: self.time })
+    pub const fn checked_add_months(self, rhs: Months) -> Option<NaiveDateTime> {
+        Some(Self { date: try_opt!(self.date.checked_add_months(rhs)), time: self.time })
     }
 
     /// Subtracts given `Duration` from the current date and time.
@@ -783,24 +786,24 @@ impl NaiveDateTime {
     /// );
     /// ```
     #[must_use]
-    pub fn checked_sub_months(self, rhs: Months) -> Option<NaiveDateTime> {
-        Some(Self { date: self.date.checked_sub_months(rhs)?, time: self.time })
+    pub const fn checked_sub_months(self, rhs: Months) -> Option<NaiveDateTime> {
+        Some(Self { date: try_opt!(self.date.checked_sub_months(rhs)), time: self.time })
     }
 
     /// Add a duration in [`Days`] to the date part of the `NaiveDateTime`
     ///
     /// Returns `None` if the resulting date would be out of range.
     #[must_use]
-    pub fn checked_add_days(self, days: Days) -> Option<Self> {
-        Some(Self { date: self.date.checked_add_days(days)?, ..self })
+    pub const fn checked_add_days(self, days: Days) -> Option<Self> {
+        Some(Self { date: try_opt!(self.date.checked_add_days(days)), ..self })
     }
 
     /// Subtract a duration in [`Days`] from the date part of the `NaiveDateTime`
     ///
     /// Returns `None` if the resulting date would be out of range.
     #[must_use]
-    pub fn checked_sub_days(self, days: Days) -> Option<Self> {
-        Some(Self { date: self.date.checked_sub_days(days)?, ..self })
+    pub const fn checked_sub_days(self, days: Days) -> Option<Self> {
+        Some(Self { date: try_opt!(self.date.checked_sub_days(days)), ..self })
     }
 
     /// Subtracts another `NaiveDateTime` from the current date and time.