internal/core/adt: prepare to differentiate types of arcs and notify

Currently both arrays use ccArc. But this
is confusing as not all fields are used by both.
This makes the dependency code more complex
than necessary. It will result in a bit more code,
but allows for more clarity in further refactoring.

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I35e84d0831433ad88e7a9773c36642b483285e7b
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1207452
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>

Author: mpvl

internal/core/adt/dep.go

@@ -374,19 +374,25 @@ func (n *nodeContext) breakIncomingDeps() {
 		if src.src.IsDisjunct {
 			continue
 		}
-		var a *ccArc
 		switch r.kind {
 		case ARC:
-			a = &src.arcs[r.index]
+			a := &src.arcs[r.index]
+			if a.decremented {
+				continue
+			}
+			a.decremented = true
+
+			src.src.unify(n.ctx, needTasksDone, attemptOnly)
+			a.dst.decDependent(n.ctx, ARC, src)
 		case NOTIFY:
-			a = &src.notify[r.index]
+			a := &src.notify[r.index]
+			if a.decremented {
+				continue
+			}
+			a.decremented = true
+
+			src.src.unify(n.ctx, needTasksDone, attemptOnly)
+			a.dst.decDependent(n.ctx, NOTIFY, src)
 		}
-		if a.decremented {
-			continue
-		}
-		a.decremented = true
-
-		src.src.unify(n.ctx, needTasksDone, attemptOnly)
-		a.dst.decDependent(n.ctx, r.kind, src)
 	}
 }