Make internal functions returning Weekday const

Author: pitdicker

src/naive/internals.rs

@@ -17,7 +17,6 @@
 
 use crate::Weekday;
 use core::{fmt, i32};
-use num_traits::FromPrimitive;
 
 /// The internal date representation. This also includes the packed `Mdf` value.
 pub(super) type DateImpl = i32;
@@ -320,17 +319,17 @@ impl Of {
     }
 
     #[inline]
-    pub(super) fn weekday(&self) -> Weekday {
+    pub(super) const fn weekday(&self) -> Weekday {
         let Of(of) = *self;
-        Weekday::from_u32(((of >> 4) + (of & 0b111)) % 7).unwrap()
+        Weekday::from_u32_mod7((of >> 4) + (of & 0b111))
     }
 
     #[inline]
     pub(super) fn isoweekdate_raw(&self) -> (u32, Weekday) {
         // week ordinal = ordinal + delta
         let Of(of) = *self;
         let weekord = (of >> 4).wrapping_add(self.flags().isoweek_delta());
-        (weekord / 7, Weekday::from_u32(weekord % 7).unwrap())
+        (weekord / 7, Weekday::from_u32_mod7(weekord))
     }
 
     #[cfg_attr(feature = "cargo-clippy", allow(clippy::wrong_self_convention))]

src/weekday.rs

@@ -50,14 +50,29 @@ pub enum Weekday {
 }
 
 impl Weekday {
+    /// Create a `Weekday` from an `u32`, with Monday = 0.
+    /// Infallible, takes `n % 7`.
+    #[inline]
+    pub(crate) const fn from_u32_mod7(n: u32) -> Weekday {
+        match n % 7 {
+            0 => Weekday::Mon,
+            1 => Weekday::Tue,
+            2 => Weekday::Wed,
+            3 => Weekday::Thu,
+            4 => Weekday::Fri,
+            5 => Weekday::Sat,
+            _ => Weekday::Sun,
+        }
+    }
+
     /// The next day in the week.
     ///
     /// `w`:        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
     /// ----------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
     /// `w.succ()`: | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun` | `Mon`
     #[inline]
     #[must_use]
-    pub fn succ(&self) -> Weekday {
+    pub const fn succ(&self) -> Weekday {
         match *self {
             Weekday::Mon => Weekday::Tue,
             Weekday::Tue => Weekday::Wed,
@@ -76,7 +91,7 @@ impl Weekday {
     /// `w.pred()`: | `Sun` | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat`
     #[inline]
     #[must_use]
-    pub fn pred(&self) -> Weekday {
+    pub const fn pred(&self) -> Weekday {
         match *self {
             Weekday::Mon => Weekday::Sun,
             Weekday::Tue => Weekday::Mon,