Avoid generating QueryMap::extend for each key type

compiler/rustc_query_system/src/query/plumbing.rs

@@ -125,18 +125,15 @@ where
         // We use try_lock_shards here since we are called from the
         // deadlock handler, and this shouldn't be locked.
         let shards = self.shards.try_lock_shards()?;
-        let shards = shards.iter().enumerate();
-        jobs.extend(shards.flat_map(|(shard_id, shard)| {
-            shard.active.iter().filter_map(move |(k, v)| {
+        for (shard_id, shard) in shards.iter().enumerate() {
+            for (k, v) in shard.active.iter() {
                 if let QueryResult::Started(ref job) = *v {
                     let id = QueryJobId::new(job.id, shard_id, kind);
                     let info = QueryInfo { span: job.span, query: make_query(tcx, k.clone()) };
-                    Some((id, QueryJobInfo { info, job: job.clone() }))
-                } else {
-                    None
+                    jobs.insert(id, QueryJobInfo { info, job: job.clone() });
                 }
-            })
-        }));
+            }
+        }
 
         Some(())
     }