Reuse frozen inspection mapping lookups

internal/engine/document_lookup.go

@@ -7,7 +7,7 @@ type documentLookup struct {
 	byNode map[*document.Node]map[string]int
 }
 
-func buildDocumentLookup(root *document.Node) *documentLookup {
+func buildDocumentLookup(roots ...*document.Node) *documentLookup {
 	lookup := &documentLookup{byNode: make(map[*document.Node]map[string]int)}
 	visited := make(map[*document.Node]struct{})
 	var visit func(*document.Node)
@@ -35,7 +35,9 @@ func buildDocumentLookup(root *document.Node) *documentLookup {
 			}
 		}
 	}
-	visit(root)
+	for _, root := range roots {
+		visit(root)
+	}
 	return lookup
 }