Re-add comments

Author: pierwill

chalk-solve/src/coherence.rs

@@ -109,6 +109,9 @@ where
 
         let node_impls: Vec<ImplId<_>> = forest.raw_nodes().iter().map(|x| x.weight).collect();
 
+        // Find all specializations (implemented in coherence/solve)
+        // Record them in the forest by adding an edge from the less special
+        // to the more special.
         self.visit_specializations_of_trait(|less_special, more_special| {
             // Check so that we never add multiple nodes with the same ImplId.
             if !node_impls.contains(&less_special) && !node_impls.contains(&more_special) {