Add tab tooltips

crates/diagnostics/src/diagnostics.rs

@@ -24,6 +24,7 @@ use settings::Settings;
 use smallvec::SmallVec;
 use std::{
     any::{Any, TypeId},
+    borrow::Cow,
     cmp::Ordering,
     ops::Range,
     path::PathBuf,
@@ -531,6 +532,10 @@ impl Item for ProjectDiagnosticsEditor {
             .update(cx, |editor, cx| editor.navigate(data, cx))
     }
 
+    fn tab_tooltip_text<'a>(&'a self, _: &'a AppContext) -> Option<Cow<'a, str>> {
+        Some("Project Diagnostics".into())
+    }
+
     fn is_dirty(&self, cx: &AppContext) -> bool {
         self.excerpts.read(cx).is_dirty(cx)
     }