incr.comp.: Add some comments.

[rust.git] / src / librustc / dep_graph / graph.rs

diff --git a/src/librustc/dep_graph/graph.rs b/src/librustc/dep_graph/graph.rs
index 24e190c3fb7a4e73228f9fef109762c0a9265160..90a29b6348245fb24eb7b798b7a89ce2330cf3b8 100644 (file)
--- a/src/librustc/dep_graph/graph.rs
+++ b/src/librustc/dep_graph/graph.rs
@@ -27,6 +27,14 @@
 #[derive(Clone)]
 pub struct DepGraph {
     data: Option<Rc<DepGraphData>>,
+
+    // At the moment we are using DepNode as key here. In the future it might
+    // be possible to use an IndexVec<DepNodeIndex, _> here. At the moment there
+    // are a few problems with that:
+    // - Some fingerprints are needed even if incr. comp. is disabled -- yet
+    //   we need to have a dep-graph to generate DepNodeIndices.
+    // - The architecture is still in flux and it's not clear what how to best
+    //   implement things.
     fingerprints: Rc<RefCell<FxHashMap<DepNode, Fingerprint>>>
 }