Remove SubsecondError and replace with Option API (#6500)

Author: sffc

components/datetime/src/options/mod.rs

@@ -562,16 +562,25 @@ pub enum SubsecondDigits {
     S9 = 9,
 }
 
-/// An error from constructing [`SubsecondDigits`].
-#[derive(Debug, Copy, Clone, PartialEq, Eq, displaydoc::Display)]
-#[non_exhaustive]
-pub enum SubsecondError {
-    /// The provided value is out of range (1-9).
-    OutOfRange,
+impl SubsecondDigits {
+    /// Constructs a [`SubsecondDigits`] from an integer number of digits.
+    pub fn try_from_int(value: u8) -> Option<Self> {
+        use SubsecondDigits::*;
+        match value {
+            1 => Some(S1),
+            2 => Some(S2),
+            3 => Some(S3),
+            4 => Some(S4),
+            5 => Some(S5),
+            6 => Some(S6),
+            7 => Some(S7),
+            8 => Some(S8),
+            9 => Some(S9),
+            _ => None,
+        }
+    }
 }
 
-impl core::error::Error for SubsecondError {}
-
 impl From<SubsecondDigits> for u8 {
     fn from(value: SubsecondDigits) -> u8 {
         use SubsecondDigits::*;
@@ -588,22 +597,3 @@ impl From<SubsecondDigits> for u8 {
         }
     }
 }
-
-impl TryFrom<u8> for SubsecondDigits {
-    type Error = SubsecondError;
-    fn try_from(value: u8) -> Result<Self, Self::Error> {
-        use SubsecondDigits::*;
-        match value {
-            1 => Ok(S1),
-            2 => Ok(S2),
-            3 => Ok(S3),
-            4 => Ok(S4),
-            5 => Ok(S5),
-            6 => Ok(S6),
-            7 => Ok(S7),
-            8 => Ok(S8),
-            9 => Ok(S9),
-            _ => Err(SubsecondError::OutOfRange),
-        }
-    }
-}

ffi/capi/bindings/c/TimePrecision.h

@@ -46,6 +46,15 @@ pub mod ffi {
         Subsecond8,
         Subsecond9,
     }
+
+    impl TimePrecision {
+        #[diplomat::rust_link(icu::datetime::options::SubsecondDigits::try_from_int, FnInEnum)]
+        pub fn from_subsecond_digits(digits: u8) -> Option<Self> {
+            icu_datetime::options::SubsecondDigits::try_from_int(digits)
+                .map(icu_datetime::options::TimePrecision::Subsecond)
+                .map(Into::into)
+        }
+    }
 }
 
 impl From<ffi::TimePrecision> for icu_datetime::options::TimePrecision {
@@ -69,3 +78,29 @@ impl From<ffi::TimePrecision> for icu_datetime::options::TimePrecision {
         }
     }
 }
+
+impl From<icu_datetime::options::TimePrecision> for ffi::TimePrecision {
+    fn from(time_precision: icu_datetime::options::TimePrecision) -> Self {
+        use icu_datetime::options::SubsecondDigits;
+        use icu_datetime::options::TimePrecision;
+        match time_precision {
+            TimePrecision::Hour => ffi::TimePrecision::Hour,
+            TimePrecision::Minute => ffi::TimePrecision::Minute,
+            TimePrecision::MinuteOptional => ffi::TimePrecision::MinuteOptional,
+            TimePrecision::Second => ffi::TimePrecision::Second,
+            TimePrecision::Subsecond(SubsecondDigits::S1) => ffi::TimePrecision::Subsecond1,
+            TimePrecision::Subsecond(SubsecondDigits::S2) => ffi::TimePrecision::Subsecond2,
+            TimePrecision::Subsecond(SubsecondDigits::S3) => ffi::TimePrecision::Subsecond3,
+            TimePrecision::Subsecond(SubsecondDigits::S4) => ffi::TimePrecision::Subsecond4,
+            TimePrecision::Subsecond(SubsecondDigits::S5) => ffi::TimePrecision::Subsecond5,
+            TimePrecision::Subsecond(SubsecondDigits::S6) => ffi::TimePrecision::Subsecond6,
+            TimePrecision::Subsecond(SubsecondDigits::S7) => ffi::TimePrecision::Subsecond7,
+            TimePrecision::Subsecond(SubsecondDigits::S8) => ffi::TimePrecision::Subsecond8,
+            TimePrecision::Subsecond(SubsecondDigits::S9) => ffi::TimePrecision::Subsecond9,
+            _ => {
+                debug_assert!(false, "cross-crate exhaustive match");
+                ffi::TimePrecision::Second
+            }
+        }
+    }
+}

ffi/capi/bindings/cpp/icu4x/TimePrecision.d.hpp

@@ -15,7 +15,6 @@
 
 
 fixed_decimal::Decimal::new#FnInTypedef
-icu::datetime::options::SubsecondError#Enum
 icu_provider_adapters::fork::ForkByMarkerProvider::inner#FnInTypedef
 icu_provider_adapters::fork::ForkByMarkerProvider::inner_mut#FnInTypedef
 icu_provider_adapters::fork::ForkByMarkerProvider::into_inner#FnInTypedef