internal/core/adt: simplify linkNotify

This CL simplifies the arguments to linkNotify
to make it a bit easier to understand the invariants
that hold between various closeContexts involved.

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: Ibb38b519d947ae326ad185ee64bc1b87df457818
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1207443
Reviewed-by: Daniel Martí <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: mpvl

internal/core/adt/conjunct.go

@@ -521,6 +521,11 @@ func (n *nodeContext) insertAndSkipConjuncts(c Conjunct, id CloseInfo, depth int
 }
 
 func (n *nodeContext) addNotify2(v *Vertex, c CloseInfo) []receiver {
+	// scheduleConjunct should ensure that the closeContext of of c is aligned
+	// with v. We rely on this to be the case here. We enforce this invariant
+	// here for clarity and to ensure correctness.
+	n.ctx.Assertf(token.NoPos, c.cc.src == v, "close context not aligned with vertex")
+
 	// No need to do the notification mechanism if we are already complete.
 	old := n.notify
 	switch {
@@ -543,15 +548,15 @@ func (n *nodeContext) addNotify2(v *Vertex, c CloseInfo) []receiver {
 	}
 
 	for _, r := range n.notify {
-		if r.v == v && r.cc == c.cc {
+		if r.cc == c.cc {
 			return old
 		}
 	}
 
 	cc := c.cc
 
-	if root.linkNotify(n.ctx, v, cc, c.CycleInfo) {
-		n.notify = append(n.notify, receiver{v, cc})
+	if root.linkNotify(n.ctx, cc) {
+		n.notify = append(n.notify, receiver{cc.src, cc})
 	}
 
 	return old

internal/core/adt/eval.go

@@ -1192,6 +1192,8 @@ type nodeContextState struct {
 }
 
 // A receiver receives notifications.
+// cc is used for V3 and is nil in V2.
+// v is equal to cc.src._cc in V3.
 type receiver struct {
 	v  *Vertex
 	cc *closeContext

internal/core/adt/fields.go

@@ -463,14 +463,14 @@ func (cc *closeContext) getKeyedCC(ctx *OpContext, key *closeContext, c CycleInf
 	return arc
 }
 
-func (cc *closeContext) linkNotify(ctx *OpContext, dst *Vertex, key *closeContext, c CycleInfo) bool {
+func (cc *closeContext) linkNotify(ctx *OpContext, key *closeContext) bool {
 	for _, a := range cc.arcs {
 		if a.key == key {
 			return false
 		}
 	}
 
-	cc.addDependency(ctx, NOTIFY, false, key, key, dst.cc())
+	cc.addDependency(ctx, NOTIFY, false, key, key, key.src.cc())
 	return true
 }