Index collection policy retirement

internal/engine/compose.go

@@ -43,12 +43,20 @@ type sequenceHistoryContribution struct {
 // assemblyAccumulator owns one mutable working document. Acquired trees held by
 // history applications are separate from its root and remain unchanged.
 type assemblyAccumulator struct {
-	current *composedDocument
-	index   mappingIndex
+	current                    *composedDocument
+	index                      mappingIndex
+	collectionPolicyRetirement *collectionPolicyRetirementIndex
 }
 
 func newAssemblyAccumulator(owned *composedDocument) *assemblyAccumulator {
-	return &assemblyAccumulator{current: owned}
+	policies := collectionPolicyScope{}
+	if owned != nil {
+		policies = owned.collectionPolicies
+	}
+	return &assemblyAccumulator{
+		current:                    owned,
+		collectionPolicyRetirement: newCollectionPolicyRetirementIndex(policies),
+	}
 }
 
 // cloneComposedDocument detaches mutable composition and provenance state;