diagnostics: Reduce cloning of DiagnosticEntry (#39193)

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/language/src/buffer.rs

@@ -1,7 +1,7 @@
 use crate::{
     DebuggerTextObject, LanguageScope, Outline, OutlineConfig, RunnableCapture, RunnableTag,
     TextObject, TreeSitterOptions,
-    diagnostic_set::{DiagnosticEntry, DiagnosticGroup},
+    diagnostic_set::{DiagnosticEntry, DiagnosticEntryRef, DiagnosticGroup},
     language_settings::{LanguageSettings, language_settings},
     outline::OutlineItem,
     syntax_map::{
@@ -4519,7 +4519,7 @@ impl BufferSnapshot {
         &'a self,
         search_range: Range<T>,
         reversed: bool,
-    ) -> impl 'a + Iterator<Item = DiagnosticEntry<O>>
+    ) -> impl 'a + Iterator<Item = DiagnosticEntryRef<'a, O>>
     where
         T: 'a + Clone + ToOffset,
         O: 'a + FromAnchor,
@@ -4552,11 +4552,13 @@ impl BufferSnapshot {
                 })?;
             iterators[next_ix]
                 .next()
-                .map(|DiagnosticEntry { range, diagnostic }| DiagnosticEntry {
-                    diagnostic,
-                    range: FromAnchor::from_anchor(&range.start, self)
-                        ..FromAnchor::from_anchor(&range.end, self),
-                })
+                .map(
+                    |DiagnosticEntryRef { range, diagnostic }| DiagnosticEntryRef {
+                        diagnostic,
+                        range: FromAnchor::from_anchor(&range.start, self)
+                            ..FromAnchor::from_anchor(&range.end, self),
+                    },
+                )
         })
     }
 
@@ -4572,7 +4574,7 @@ impl BufferSnapshot {
     pub fn diagnostic_groups(
         &self,
         language_server_id: Option<LanguageServerId>,
-    ) -> Vec<(LanguageServerId, DiagnosticGroup<Anchor>)> {
+    ) -> Vec<(LanguageServerId, DiagnosticGroup<'_, Anchor>)> {
         let mut groups = Vec::new();
 
         if let Some(language_server_id) = language_server_id {
@@ -4603,7 +4605,7 @@ impl BufferSnapshot {
     pub fn diagnostic_group<O>(
         &self,
         group_id: usize,
-    ) -> impl Iterator<Item = DiagnosticEntry<O>> + '_
+    ) -> impl Iterator<Item = DiagnosticEntryRef<'_, O>> + use<'_, O>
     where
         O: FromAnchor + 'static,
     {