Give checkOwnFamily the scope walk's signature, and drop its wrapper

data.go

@@ -257,7 +257,7 @@ func checkNodeFences(s nodeScope) error {
 		return err
 	}
 	if refs {
-		if err := s(checkOwnFamilies); err != nil {
+		if err := s(checkOwnFamily); err != nil {
 			return err
 		}
 		if err := s(fence.checkDraws); err != nil {

drawfence.go

@@ -24,17 +24,6 @@ func (f *drawFence) checkDrawGroup(path string, n node) error {
 	return nil
 }
 
-func checkOwnFamilies(path string, n node) error {
-	t, ok := n.(*template)
-	if !ok {
-		return nil
-	}
-	if err := checkOwnFamily(t); err != nil {
-		return fmt.Errorf("%s: %w", path, err)
-	}
-	return nil
-}
-
 func (f *drawFence) checkDraws(path string, n node) error {
 	t, ok := n.(*template)
 	if !ok {

readsurvey.go

@@ -258,11 +258,12 @@ func checkFamilies(reads []pathRead) error {
 // read draws its row without pinning it, so the family would draw apart from the row
 // it renders, whichever draws the reaching template holds.
 // docs/decisions.md#a-table-never-reaches-its-own-family-by-any-route
-func checkOwnFamily(t *template) error {
-	own := t.site.table
-	if own == nil {
+func checkOwnFamily(path string, n node) error {
+	t, isTemplate := n.(*template)
+	if !isTemplate || t.site.table == nil {
 		return nil
 	}
+	own := t.site.table
 	seen := map[node]bool{}
 	var find func(n node) (renderEdge, *table, bool)
 	find = func(n node) (renderEdge, *table, bool) {
@@ -283,7 +284,7 @@ func checkOwnFamily(t *template) error {
 		return renderEdge{}, nil, false
 	}
 	if e, familyTable, found := find(t); found {
-		return fmt.Errorf("%s reads %s, a table of its own family, which a bare read of %s would draw apart from the row it renders; read the family from a template beside it, or add the value as a column", e.reached(), familyTable.segment, own.segment)
+		return fmt.Errorf("%s: %s reads %s, a table of its own family, which a bare read of %s would draw apart from the row it renders; read the family from a template beside it, or add the value as a column", path, e.reached(), familyTable.segment, own.segment)
 	}
 	return nil
 }