From 7e626ba9a08129b2c9e5c3d14b7890f7e1b5847c Mon Sep 17 00:00:00 2001
From: "gcp-cherry-pick-bot[bot]"
 <98988430+gcp-cherry-pick-bot[bot]@users.noreply.github.com>
Date: Fri, 26 Apr 2024 14:18:00 -0600
Subject: [PATCH] Fix panic in Diagnostics (cherry-pick #11066) (#11069)

Cherry-picked Fix panic in Diagnostics (#11066)

cc @maxbrunsfeld

Release Notes:

- Fixed a panic in populating diagnostics

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
---
 crates/diagnostics/src/diagnostics.rs | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/crates/diagnostics/src/diagnostics.rs b/crates/diagnostics/src/diagnostics.rs
index fc7f8de8a0d96c0e107194db716160004d27ba27..6e2f6129baf250eeba3e2f8a5f6c570221c53c0d 100644
--- a/crates/diagnostics/src/diagnostics.rs
+++ b/crates/diagnostics/src/diagnostics.rs
@@ -887,22 +887,27 @@ fn diagnostic_header_renderer(diagnostic: Diagnostic) -> RenderBlock {
     })
 }
 
-fn compare_diagnostics<L: language::ToOffset, R: language::ToOffset>(
-    lhs: &DiagnosticEntry<L>,
-    rhs: &DiagnosticEntry<R>,
+fn compare_diagnostics(
+    old: &DiagnosticEntry<language::Anchor>,
+    new: &DiagnosticEntry<language::Anchor>,
     snapshot: &language::BufferSnapshot,
 ) -> Ordering {
-    lhs.range
+    use language::ToOffset;
+    // The old diagnostics may point to a previously open Buffer for this file.
+    if !old.range.start.is_valid(snapshot) {
+        return Ordering::Greater;
+    }
+    old.range
         .start
         .to_offset(snapshot)
-        .cmp(&rhs.range.start.to_offset(snapshot))
+        .cmp(&new.range.start.to_offset(snapshot))
         .then_with(|| {
-            lhs.range
+            old.range
                 .end
                 .to_offset(snapshot)
-                .cmp(&rhs.range.end.to_offset(snapshot))
+                .cmp(&new.range.end.to_offset(snapshot))
         })
-        .then_with(|| lhs.diagnostic.message.cmp(&rhs.diagnostic.message))
+        .then_with(|| old.diagnostic.message.cmp(&new.diagnostic.message))
 }
 
 #[cfg(test)]