First draft for implementing Local Displayname Algorithm

components/locid/src/langid.rs

@@ -504,3 +504,101 @@ impl From<&LanguageIdentifier>
         (langid.language, langid.script, langid.region)
     }
 }
+
+/// Convert from an LS tuple to a [`LanguageIdentifier`].
+///
+/// # Examples
+///
+/// ```
+/// use icu::locid::{
+///     langid, subtags_language as language,
+///     subtags_script as script, LanguageIdentifier,
+/// };
+///
+/// let lang = language!("en");
+/// let script = script!("Latn");
+/// assert_eq!(
+///     LanguageIdentifier::from((lang, script)),
+///     langid!("en-Latn")
+/// );
+/// ```
+impl From<(subtags::Language, subtags::Script)> for LanguageIdentifier {
+    fn from(lsr: (subtags::Language, subtags::Script)) -> Self {
+        Self {
+            language: lsr.0,
+            script: Some(lsr.1),
+            ..Default::default()
+        }
+    }
+}
+
+/// Convert from a [`LanguageIdentifier`] to an LS tuple.
+///
+/// # Examples
+///
+/// ```
+/// use icu::locid::{
+///     langid, subtags_language as language,
+///     subtags_script as script,
+/// };
+///
+/// let lid = langid!("en-Latn");
+/// let (lang, script) = (&lid).into();
+///
+/// assert_eq!(lang, language!("en"));
+/// assert_eq!(script, script!("Latn"));
+/// ```
+impl From<&LanguageIdentifier> for (subtags::Language, subtags::Script) {
+    fn from(langid: &LanguageIdentifier) -> Self {
+        (langid.language, langid.script.unwrap())
+    }
+}
+
+/// Convert from an LR tuple to a [`LanguageIdentifier`].
+///
+/// # Examples
+///
+/// ```
+/// use icu::locid::{
+///     langid, subtags_language as language,
+///     subtags_region as region, LanguageIdentifier,
+/// };
+///
+/// let lang = language!("en");
+/// let region = region!("GB");
+/// assert_eq!(
+///     LanguageIdentifier::from((lang, region)),
+///     langid!("en-GB")
+/// );
+/// ```
+impl From<(subtags::Language, subtags::Region)> for LanguageIdentifier {
+    fn from(lsr: (subtags::Language, subtags::Region)) -> Self {
+        Self {
+            language: lsr.0,
+            region: Some(lsr.1),
+            ..Default::default()
+        }
+    }
+}
+
+/// Convert from a [`LanguageIdentifier`] to an LR tuple.
+///
+/// # Examples
+///
+/// ```
+/// use icu::locid::{
+///     langid, subtags_language as language,
+///     subtags_region as region,
+/// };
+///
+/// let lid = langid!("en-GB");
+/// let (lang, region) = (&lid).into();
+///
+/// assert_eq!(lang, language!("en"));
+/// assert_eq!(region, region!("GB"));
+/// ```
+impl From<&LanguageIdentifier> for (subtags::Language, subtags::Region) {
+    fn from(langid: &LanguageIdentifier) -> Self {
+        (langid.language, langid.region.unwrap())
+    }
+}

experimental/displaynames/Cargo.toml

@@ -47,3 +47,7 @@ icu_testdata = { path = "../../provider/testdata", default-features = false, fea
 std = ["icu_collections/std", "icu_locid/std", "icu_provider/std"]
 serde = ["dep:serde", "zerovec/serde", "icu_collections/serde", "tinystr/serde", "icu_provider/serde"]
 datagen = ["serde", "std", "dep:databake", "zerovec/databake", "icu_collections/databake", "tinystr/databake"]
+
+[[test]]
+name = "tests"
+path = "tests/tests.rs"