Keep the placement ask among the assigner's asks: its Approve's level, not its kind, needs the proof (ADR 0567 §5, issue 1126)

go/delivery/view_answers.go

@@ -39,7 +39,8 @@ const (
 	// a composition judged to recreate a container or move data, or one that cannot be judged (ADR 0539 clause 14).
 	AskKindRecord = "record"
 	// AskKindPlacement is the kind of the seat mesh-placement's authorising ask about a proposal (novox/hq ADR 0567 §5):
-	// `placement.<proposal id>`. Its yes is an Approve that only a channel proving who answered takes, never the view.
+	// `placement.<proposal id>`. The kind needs no proof, as the bus's put does not: its yes is an Approve, which only a
+	// channel proving who answered takes and the view never does (ViewAnswerFits).
 	AskKindPlacement = "placement"
 
 	viewWord = "view"
@@ -63,9 +64,9 @@ type AskKey struct {
 // merge's Approve does (ADR 0421 §1, issue 953), the assigner's hold and restore do not. An unknown kind is refused.
 func AskNeedsProof(kind string) (bool, error) {
 	switch kind {
-	case AskKindMerge, AskKindPlacement:
+	case AskKindMerge:
 		return true, nil
-	case AskKindHold, AskKindRestore, AskKindBackup, AskKindRecord:
+	case AskKindHold, AskKindRestore, AskKindBackup, AskKindRecord, AskKindPlacement:
 		return false, nil
 	}
 	return false, fmt.Errorf("delivery: %q is not a kind of ask, %s, %s, %s, %s, %s or %s", kind, AskKindMerge, AskKindHold,

go/delivery/view_answers_test.go

@@ -37,8 +37,8 @@ func TestParseAnyAskKey(t *testing.T) {
 	if err != nil || placement != "placement.p-one" {
 		t.Fatalf("PlacementAskKey = %q, %v", placement, err)
 	}
-	if proof, err := AskNeedsProof(AskKindPlacement); !proof || err != nil {
-		t.Error("a placement ask may be answered without proof of who answered")
+	if proof, err := AskNeedsProof(AskKindPlacement); proof || err != nil {
+		t.Error("the assigner cannot keep a placement ask: its kind needs proof (its yes's level does)")
 	}
 	for key, want := range map[string]AskKey{
 		hold:      {Kind: AskKindHold, Module: "mesh-mail", FP: fp},