Add some assertions

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -970,6 +970,7 @@ impl<K: DepKind> DepGraph<K> {
     }
 
     pub(crate) fn next_virtual_depnode_index(&self) -> DepNodeIndex {
+        debug_assert!(self.data.is_none());
         let index = self.virtual_dep_node_index.fetch_add(1, Relaxed);
         DepNodeIndex::from_u32(index)
     }

compiler/rustc_query_system/src/query/plumbing.rs

@@ -429,6 +429,8 @@ where
     Q: QueryConfig<Qcx>,
     Qcx: QueryContext,
 {
+    debug_assert!(!qcx.dep_context().dep_graph().is_fully_enabled());
+
     // Fingerprint the key, just to assert that it doesn't
     // have anything we don't consider hashable
     if cfg!(debug_assertions) {