Assembling requested_families earlier (#5043)

Author: robertbastian

components/locale_core/src/langid.rs

@@ -144,6 +144,14 @@ impl LanguageIdentifier {
         variants: subtags::Variants::new(),
     };
 
+    /// Whether this language identifier equals [`Self::UND`].
+    pub const fn is_empty(&self) -> bool {
+        self.language.is_empty()
+            && self.script.is_none()
+            && self.region.is_none()
+            && self.variants.is_empty()
+    }
+
     /// This is a best-effort operation that performs all available levels of canonicalization.
     ///
     /// At the moment the operation will normalize casing and the separator, but in the future

components/locale_core/src/shortvec/mod.rs

@@ -130,7 +130,7 @@ impl<T> ShortBoxSlice<T> {
 
     /// Returns whether the collection is empty.
     #[inline]
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         use ShortBoxSliceInner::*;
         matches!(self.0, ZeroOne(None))
     }

components/locale_core/src/subtags/language.rs

@@ -95,8 +95,8 @@ impl Language {
     /// assert!(lang.is_empty());
     /// ```
     #[inline]
-    pub fn is_empty(self) -> bool {
-        self == Self::UND
+    pub const fn is_empty(self) -> bool {
+        matches!(self, Self::UND)
     }
 }
 

components/locale_core/src/subtags/variants.rs

@@ -109,6 +109,11 @@ impl Variants {
         core::mem::take(self)
     }
 
+    /// Whether the list of variants is empty.
+    pub const fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+
     pub(crate) fn for_each_subtag_str<E, F>(&self, f: &mut F) -> Result<(), E>
     where
         F: FnMut(&str) -> Result<(), E>,