1 files changed, 4 insertions, 0 deletions
diff --git a/compiler/rustc_query_system/src/query/caches.rs b/compiler/rustc_query_system/src/query/caches.rs
index cdd43572422..4c4680b5d8e 100644
--- a/compiler/rustc_query_system/src/query/caches.rs
+++ b/compiler/rustc_query_system/src/query/caches.rs
@@ -117,6 +117,8 @@ where
         let mut lock = self.cache.get_shard_by_value(&key).lock();
         #[cfg(not(parallel_compiler))]
         let mut lock = self.cache.lock();
+        // We may be overwriting another value.  This is all right, since the dep-graph
+        // will check that the fingerprint matches.
         lock.insert(key, (value.clone(), index));
         value
     }
@@ -202,6 +204,8 @@ where
         let mut lock = self.cache.get_shard_by_value(&key).lock();
         #[cfg(not(parallel_compiler))]
         let mut lock = self.cache.lock();
+        // We may be overwriting another value.  This is all right, since the dep-graph
+        // will check that the fingerprint matches.
         lock.insert(key, value);
         &value.0
     }