Make Mdf methods fallible in the face of invalid input

Author: djc

src/naive/date.rs

@@ -267,7 +267,7 @@ impl NaiveDate {
     /// ```
     pub fn from_ymd_opt(year: i32, month: u32, day: u32) -> Option<NaiveDate> {
         let flags = YearFlags::from_year(year);
-        NaiveDate::from_mdf(year, Mdf::new(month, day, flags))
+        NaiveDate::from_mdf(year, Mdf::new(month, day, flags)?)
     }
 
     /// Makes a new `NaiveDate` from the [ordinal date](#ordinal-date)
@@ -615,7 +615,7 @@ impl NaiveDate {
         let days = [31, feb_days, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
         let day = Ord::min(self.day(), days[(month - 1) as usize]);
 
-        NaiveDate::from_mdf(year, Mdf::new(month as u32, day, flags))
+        NaiveDate::from_mdf(year, Mdf::new(month as u32, day, flags)?)
     }
 
     /// Add a duration in [`Days`] to the date
@@ -1429,7 +1429,7 @@ impl Datelike for NaiveDate {
     /// ```
     #[inline]
     fn with_month(&self, month: u32) -> Option<NaiveDate> {
-        self.with_mdf(self.mdf().with_month(month))
+        self.with_mdf(self.mdf().with_month(month)?)
     }
 
     /// Makes a new `NaiveDate` with the month number (starting from 0) changed.
@@ -1448,7 +1448,7 @@ impl Datelike for NaiveDate {
     /// ```
     #[inline]
     fn with_month0(&self, month0: u32) -> Option<NaiveDate> {
-        self.with_mdf(self.mdf().with_month(month0 + 1))
+        self.with_mdf(self.mdf().with_month(month0 + 1)?)
     }
 
     /// Makes a new `NaiveDate` with the day of month (starting from 1) changed.
@@ -1467,7 +1467,7 @@ impl Datelike for NaiveDate {
     /// ```
     #[inline]
     fn with_day(&self, day: u32) -> Option<NaiveDate> {
-        self.with_mdf(self.mdf().with_day(day))
+        self.with_mdf(self.mdf().with_day(day)?)
     }
 
     /// Makes a new `NaiveDate` with the day of month (starting from 0) changed.
@@ -1486,7 +1486,7 @@ impl Datelike for NaiveDate {
     /// ```
     #[inline]
     fn with_day0(&self, day0: u32) -> Option<NaiveDate> {
-        self.with_mdf(self.mdf().with_day(day0 + 1))
+        self.with_mdf(self.mdf().with_day(day0 + 1)?)
     }
 
     /// Makes a new `NaiveDate` with the day of year (starting from 1) changed.

src/naive/internals.rs

@@ -371,30 +371,13 @@ pub(super) struct Mdf(pub(super) u32);
 
 impl Mdf {
     #[inline]
-    fn clamp_month(month: u32) -> u32 {
-        if month > 12 {
-            0
-        } else {
-            month
-        }
-    }
-
-    #[inline]
-    fn clamp_day(day: u32) -> u32 {
-        if day > 31 {
-            0
-        } else {
-            day
+    pub(super) fn new(month: u32, day: u32, YearFlags(flags): YearFlags) -> Option<Mdf> {
+        match month <= 12 && day <= 31 {
+            true => Some(Mdf((month << 9) | (day << 4) | u32::from(flags))),
+            false => None,
         }
     }
 
-    #[inline]
-    pub(super) fn new(month: u32, day: u32, YearFlags(flags): YearFlags) -> Mdf {
-        let month = Mdf::clamp_month(month);
-        let day = Mdf::clamp_day(day);
-        Mdf((month << 9) | (day << 4) | u32::from(flags))
-    }
-
     #[inline]
     pub(super) fn from_of(Of(of): Of) -> Mdf {
         let ol = of >> 3;
@@ -421,10 +404,13 @@ impl Mdf {
     }
 
     #[inline]
-    pub(super) fn with_month(&self, month: u32) -> Mdf {
-        let month = Mdf::clamp_month(month);
+    pub(super) fn with_month(&self, month: u32) -> Option<Mdf> {
+        if month > 12 {
+            return None;
+        }
+
         let Mdf(mdf) = *self;
-        Mdf((mdf & 0b1_1111_1111) | (month << 9))
+        Some(Mdf((mdf & 0b1_1111_1111) | (month << 9)))
     }
 
     #[inline]
@@ -434,10 +420,13 @@ impl Mdf {
     }
 
     #[inline]
-    pub(super) fn with_day(&self, day: u32) -> Mdf {
-        let day = Mdf::clamp_day(day);
+    pub(super) fn with_day(&self, day: u32) -> Option<Mdf> {
+        if day > 31 {
+            return None;
+        }
+
         let Mdf(mdf) = *self;
-        Mdf((mdf & !0b1_1111_0000) | (day << 4))
+        Some(Mdf((mdf & !0b1_1111_0000) | (day << 4)))
     }
 
     #[inline]
@@ -556,7 +545,12 @@ mod tests {
         fn check(expected: bool, flags: YearFlags, month1: u32, day1: u32, month2: u32, day2: u32) {
             for month in range_inclusive(month1, month2) {
                 for day in range_inclusive(day1, day2) {
-                    let mdf = Mdf::new(month, day, flags);
+                    let mdf = match Mdf::new(month, day, flags) {
+                        Some(mdf) => mdf,
+                        None if !expected => continue,
+                        None => panic!("Mdf::new({}, {}, {:?}) returned None", month, day, flags),
+                    };
+
                     assert!(
                         mdf.valid() == expected,
                         "month {} day {} = {:?} should be {} for dominical year {:?}",
@@ -711,7 +705,11 @@ mod tests {
         for &flags in FLAGS.iter() {
             for month in range_inclusive(1u32, 12) {
                 for day in range_inclusive(1u32, 31) {
-                    let mdf = Mdf::new(month, day, flags);
+                    let mdf = match Mdf::new(month, day, flags) {
+                        Some(mdf) => mdf,
+                        None => continue,
+                    };
+
                     if mdf.valid() {
                         assert_eq!(mdf.month(), month);
                         assert_eq!(mdf.day(), day);
@@ -724,20 +722,28 @@ mod tests {
     #[test]
     fn test_mdf_with_fields() {
         fn check(flags: YearFlags, month: u32, day: u32) {
-            let mdf = Mdf::new(month, day, flags);
+            let mdf = Mdf::new(month, day, flags).unwrap();
 
             for month in range_inclusive(0u32, 16) {
-                let mdf = mdf.with_month(month);
-                assert_eq!(mdf.valid(), Mdf::new(month, day, flags).valid());
+                let mdf = match mdf.with_month(month) {
+                    Some(mdf) => mdf,
+                    None if month > 12 => continue,
+                    None => panic!("failed to create Mdf with month {}", month),
+                };
+
                 if mdf.valid() {
                     assert_eq!(mdf.month(), month);
                     assert_eq!(mdf.day(), day);
                 }
             }
 
             for day in range_inclusive(0u32, 1024) {
-                let mdf = mdf.with_day(day);
-                assert_eq!(mdf.valid(), Mdf::new(month, day, flags).valid());
+                let mdf = match mdf.with_day(day) {
+                    Some(mdf) => mdf,
+                    None if day > 31 => continue,
+                    None => panic!("failed to create Mdf with month {}", month),
+                };
+
                 if mdf.valid() {
                     assert_eq!(mdf.month(), month);
                     assert_eq!(mdf.day(), day);