Clarify comment

Author: odersky

compiler/src/dotty/tools/dotc/core/TypeOps.scala

@@ -215,13 +215,13 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
       // So we need to widen `C` first. But how to decide this in general?
       // In the algorithm below, we try to widen both sides (once), and then proceed as follows:
       //
-      //  0. If no widening succeeds, proceed with step 3.
-      //  1. If only one widening succeeds, pick that one.
-      //  2. If the two widened types are in a subtype relationship, pick the smaller one.
-      //  3. If exactly one of the two types is a singleton type, pick that one.
-      //  4. If the widened tp1 is a supertype of tp2, pick widened tp1.
-      //  5. If the widened tp2 is a supertype of tp1, pick widened tp2.
-      //  6. Otherwise, pick tp1
+      //  2.0. If no widening succeeds, proceed with step 3.
+      //  2.1. If only one widening succeeds, pick that one.
+      //  2.2. If the two widened types are in a subtype relationship, pick the smaller one.
+      //  2.3. If exactly one of the two types is a singleton type, pick that one.
+      //  2.4. If the widened tp1 is a supertype of tp2, pick widened tp1.
+      //  2.5. If the widened tp2 is a supertype of tp1, pick widened tp2.
+      //  2.6. Otherwise, pick tp1
       //
       // At steps 4-6 we lose possible solutions, since we have to make an
       // arbitrary choice which side to widen. A better solution would look at