Use 32-bit arithmetic for days (#7796)

Fixes #7771


## Changelog: N/A

Unreleased API, internal change.

Author: Manishearth

components/calendar/fuzz/fuzz_targets/add.rs

@@ -26,7 +26,7 @@ pub struct DateDuration {
     pub years: u32,
     pub months: u32,
     pub weeks: u32,
-    pub days: u64,
+    pub days: u32,
 }
 
 impl From<DateDuration> for icu_calendar::types::DateDuration {

components/calendar/src/cal/coptic.rs

@@ -67,7 +67,7 @@ impl DateFieldsResolver for Coptic {
     }
 
     #[inline]
-    fn min_months_from(_start: Self::YearInfo, years: i64) -> i64 {
+    fn min_months_from(_start: Self::YearInfo, years: i32) -> i32 {
         13 * years
     }
 

components/calendar/src/cal/east_asian_traditional.rs

@@ -615,7 +615,7 @@ impl<R: Rules> DateFieldsResolver for EastAsianTraditional<R> {
     }
 
     #[inline]
-    fn min_months_from(_start: Self::YearInfo, years: i64) -> i64 {
+    fn min_months_from(_start: Self::YearInfo, years: i32) -> i32 {
         // By Rules invariant
         12 * years + (years / 3)
     }
@@ -1220,8 +1220,8 @@ mod test {
                 (largest.to_extended_year() - smallest.to_extended_year() + 1) * 12 + num_leap;
             let approximated = EastAsianTraditional::<R>::min_months_from(
                 smallest,
-                (largest.to_extended_year() - smallest.to_extended_year()) as i64 + 1,
-            ) as i32;
+                (largest.to_extended_year() - smallest.to_extended_year()) + 1,
+            );
 
             println!(
                 "absolute error {}: {}",

components/calendar/src/cal/ethiopian.rs

@@ -95,7 +95,7 @@ impl DateFieldsResolver for Ethiopian {
     }
 
     #[inline]
-    fn min_months_from(start: Self::YearInfo, years: i64) -> i64 {
+    fn min_months_from(start: Self::YearInfo, years: i32) -> i32 {
         Coptic::min_months_from(start, years)
     }
 

components/calendar/src/cal/hebrew.rs

@@ -135,7 +135,7 @@ impl DateFieldsResolver for Hebrew {
     }
 
     #[inline]
-    fn min_months_from(_start: HebrewYear, years: i64) -> i64 {
+    fn min_months_from(_start: HebrewYear, years: i32) -> i32 {
         // The Hebrew Metonic cycle is 7 leap years every 19 years,
         // which comes out to 235 months per 19 years.
         //