Refactor to use SharedString in more places (#23813)

Splitting this off from
https://github.com/zed-industries/zed/pull/23808, per @maxdeviant's
suggestion!

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/language/src/buffer_tests.rs

@@ -2424,7 +2424,7 @@ fn test_language_at_with_hidden_languages(cx: &mut App) {
             assert_eq!(config.language_name(), "Markdown".into());
 
             let language = snapshot.language_at(point).unwrap();
-            assert_eq!(language.name().0.as_ref(), "Markdown");
+            assert_eq!(language.name().as_ref(), "Markdown");
         }
 
         buffer

crates/language/src/language.rs

@@ -256,7 +256,7 @@ impl CachedLspAdapter {
 
     pub fn language_id(&self, language_name: &LanguageName) -> String {
         self.language_ids
-            .get(language_name.0.as_ref())
+            .get(language_name.as_ref())
             .cloned()
             .unwrap_or_else(|| language_name.lsp_id())
     }
@@ -1462,7 +1462,7 @@ impl Language {
         self.config
             .code_fence_block_name
             .clone()
-            .unwrap_or_else(|| self.config.name.0.to_lowercase().into())
+            .unwrap_or_else(|| self.config.name.as_ref().to_lowercase().into())
     }
 
     pub fn context_provider(&self) -> Option<Arc<dyn ContextProvider>> {

crates/language/src/language_registry.rs

@@ -14,7 +14,7 @@ use futures::{
     Future,
 };
 use globset::GlobSet;
-use gpui::{App, BackgroundExecutor};
+use gpui::{App, BackgroundExecutor, SharedString};
 use lsp::LanguageServerId;
 use parking_lot::{Mutex, RwLock};
 use postage::watch;
@@ -36,15 +36,15 @@ use util::{maybe, paths::PathExt, post_inc, ResultExt};
 #[derive(
     Debug, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize, JsonSchema,
 )]
-pub struct LanguageName(pub Arc<str>);
+pub struct LanguageName(SharedString);
 
 impl LanguageName {
     pub fn new(s: &str) -> Self {
-        Self(Arc::from(s))
+        Self(SharedString::new(s))
     }
 
     pub fn from_proto(s: String) -> Self {
-        Self(Arc::from(s))
+        Self(SharedString::from(s))
     }
     pub fn to_proto(self) -> String {
         self.0.to_string()
@@ -57,6 +57,18 @@ impl LanguageName {
     }
 }
 
+impl From<LanguageName> for SharedString {
+    fn from(value: LanguageName) -> Self {
+        value.0
+    }
+}
+
+impl AsRef<str> for LanguageName {
+    fn as_ref(&self) -> &str {
+        self.0.as_ref()
+    }
+}
+
 impl Borrow<str> for LanguageName {
     fn borrow(&self) -> &str {
         self.0.as_ref()
@@ -71,7 +83,7 @@ impl std::fmt::Display for LanguageName {
 
 impl<'a> From<&'a str> for LanguageName {
     fn from(str: &'a str) -> LanguageName {
-        LanguageName(str.into())
+        LanguageName(SharedString::new(str))
     }
 }
 
@@ -657,7 +669,7 @@ impl LanguageRegistry {
                 .iter()
                 .any(|suffix| path_suffixes.contains(&Some(suffix.as_str())));
             let custom_suffixes = user_file_types
-                .and_then(|types| types.get(&language_name.0))
+                .and_then(|types| types.get(language_name.as_ref()))
                 .unwrap_or(&empty);
             let path_matches_custom_suffix = path_suffixes
                 .iter()