Render a repeat iteration in no group, refuse a group that names nothing, key group names by category, and own reference overlap in one fence

inline.go

@@ -136,6 +136,9 @@ func inputValue(input string) (any, error) {
 // bindInline links an inline node's references against root and runs check over it, naming its
 // nodes from label.
 func bindInline(n node, label string, root map[string]node, check func(nodeScope) error) error {
+	if t, isTemplate := n.(*template); isTemplate && t.group != "" {
+		return fmt.Errorf("%s: group %q names nothing, since nothing can reference an inline template; drop it", label, t.group)
+	}
 	scope := inlineScope(n, label)
 	if err := linkNodeRefs(scope, root); err != nil {
 		return err
@@ -151,6 +154,7 @@ func linkNodeRefs(scope nodeScope, root map[string]node) error {
 		if !ok {
 			return nil
 		}
+		t.keyGroup("")
 		for _, name := range refTokens(t.format) {
 			sigil, rest, err := refShape(name)
 			if err != nil {