Add AsRef<LocaleExpander> to LocaleDirectionality (#5704)

Fixes #5297


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CHANGELOG.md

@@ -13,6 +13,7 @@
   - `icu_experimental`
   - `icu_locale`
     - New crate
+    - Allow `LocaleDirectionality` to wrap a `LocaleExpander` with user-controlled storage (https://github.com/unicode-org/icu4x/pull/5704)
   - `icu_locale_core`
     - New crate, renamed from `icu_locid`
     - Removed `Ord` and `PartialOrd` impl from `extensions::unicode::Unicode` (https://github.com/unicode-org/icu4x/pull/5617)

components/locale/src/directionality.rs

@@ -22,6 +22,8 @@ pub enum Direction {
 
 /// Provides methods to determine the direction of a locale.
 ///
+/// The `Expander` generic parameter wraps a [`LocaleExpander`].
+///
 /// # Examples
 ///
 /// ```
@@ -32,32 +34,31 @@ pub enum Direction {
 /// assert_eq!(ld.get(&langid!("en")), Some(Direction::LeftToRight));
 /// ```
 #[derive(Debug)]
-pub struct LocaleDirectionality {
+pub struct LocaleDirectionality<Expander = LocaleExpander> {
     script_direction: DataPayload<ScriptDirectionV1Marker>,
-    expander: LocaleExpander,
+    expander: Expander,
 }
 
 #[cfg(feature = "compiled_data")]
-impl Default for LocaleDirectionality {
+impl Default for LocaleDirectionality<LocaleExpander> {
     fn default() -> Self {
         Self::new()
     }
 }
 
-impl LocaleDirectionality {
+impl LocaleDirectionality<LocaleExpander> {
     /// Creates a [`LocaleDirectionality`] from compiled data.
     ///
     /// This includes limited likely subtags data, see [`LocaleExpander::new()`].
     #[cfg(feature = "compiled_data")]
     pub const fn new() -> Self {
         Self::new_with_expander(LocaleExpander::new())
     }
-
     // Note: This is a custom impl because the bounds on `try_new_unstable` don't suffice
     #[doc = icu_provider::gen_any_buffer_unstable_docs!(ANY, Self::new)]
     pub fn try_new_with_any_provider(
         provider: &(impl AnyProvider + ?Sized),
-    ) -> Result<LocaleDirectionality, DataError> {
+    ) -> Result<Self, DataError> {
         let expander = LocaleExpander::try_new_with_any_provider(provider)?;
         Self::try_new_with_expander_unstable(&provider.as_downcasting(), expander)
     }
@@ -67,11 +68,10 @@ impl LocaleDirectionality {
     #[cfg(feature = "serde")]
     pub fn try_new_with_buffer_provider(
         provider: &(impl BufferProvider + ?Sized),
-    ) -> Result<LocaleDirectionality, DataError> {
+    ) -> Result<Self, DataError> {
         let expander = LocaleExpander::try_new_with_buffer_provider(provider)?;
         Self::try_new_with_expander_unstable(&provider.as_deserializing(), expander)
     }
-
     #[doc = icu_provider::gen_any_buffer_unstable_docs!(UNSTABLE, Self::new)]
     pub fn try_new_unstable<P>(provider: &P) -> Result<LocaleDirectionality, DataError>
     where
@@ -83,7 +83,9 @@ impl LocaleDirectionality {
         let expander = LocaleExpander::try_new_unstable(provider)?;
         Self::try_new_with_expander_unstable(provider, expander)
     }
+}
 
+impl<Expander: AsRef<LocaleExpander>> LocaleDirectionality<Expander> {
     /// Creates a [`LocaleDirectionality`] with a custom [`LocaleExpander`] and compiled data.
     ///
     /// This allows using [`LocaleExpander::new_extended()`] with data for all locales.
@@ -108,7 +110,7 @@ impl LocaleDirectionality {
     /// );
     /// ```
     #[cfg(feature = "compiled_data")]
-    pub const fn new_with_expander(expander: LocaleExpander) -> Self {
+    pub const fn new_with_expander(expander: Expander) -> Self {
         LocaleDirectionality {
             script_direction: DataPayload::from_static_ref(
                 crate::provider::Baked::SINGLETON_SCRIPT_DIRECTION_V1_MARKER,
@@ -120,8 +122,8 @@ impl LocaleDirectionality {
     #[doc = icu_provider::gen_any_buffer_unstable_docs!(UNSTABLE, Self::new_with_expander)]
     pub fn try_new_with_expander_unstable<P>(
         provider: &P,
-        expander: LocaleExpander,
-    ) -> Result<LocaleDirectionality, DataError>
+        expander: Expander,
+    ) -> Result<Self, DataError>
     where
         P: DataProvider<ScriptDirectionV1Marker> + ?Sized,
     {
@@ -177,7 +179,7 @@ impl LocaleDirectionality {
     /// );
     /// ```
     pub fn get(&self, langid: &LanguageIdentifier) -> Option<Direction> {
-        let script = self.expander.get_likely_script(langid)?;
+        let script = self.expander.as_ref().get_likely_script(langid)?;
 
         if self.script_in_ltr(script) {
             Some(Direction::LeftToRight)
@@ -197,6 +199,7 @@ impl LocaleDirectionality {
     /// See [`LocaleDirectionality::get`] for more information.
     pub fn is_right_to_left(&self, langid: &LanguageIdentifier) -> bool {
         self.expander
+            .as_ref()
             .get_likely_script(langid)
             .map(|s| self.script_in_rtl(s))
             .unwrap_or(false)
@@ -211,6 +214,7 @@ impl LocaleDirectionality {
     /// See [`LocaleDirectionality::get`] for more information.
     pub fn is_left_to_right(&self, langid: &LanguageIdentifier) -> bool {
         self.expander
+            .as_ref()
             .get_likely_script(langid)
             .map(|s| self.script_in_ltr(s))
             .unwrap_or(false)

components/locale/src/expander.rs

@@ -582,6 +582,12 @@ impl LocaleExpander {
     }
 }
 
+impl AsRef<LocaleExpander> for LocaleExpander {
+    fn as_ref(&self) -> &LocaleExpander {
+        self
+    }
+}
+
 #[cfg(feature = "serde")]
 #[cfg(test)]
 mod tests {