Answer architecture round 2: linkTemplates' doc says which steps pass names as arguments, checkEveryNameRead, and an invariant guard on a binding with no read at link

link.go

@@ -62,8 +62,8 @@ type linkedNames struct {
 }
 
 // linkTemplates links ts in steps, each over every template before the next starts, each
-// returning what it builds and taking what an earlier step built as an argument: the references,
-// the names' targets, the compiled formats, the keys and reads of each name, and the column each
+// returning what it builds: the references and the compiled formats, kept on each template, the
+// names' targets, keys and reads, passed to the steps after as arguments, and the column each
 // format reads. The bindings take their targets and keys once every check has passed.
 func linkTemplates(ts []linkSite, root map[string]node) error {
 	for _, s := range ts {

name.go

@@ -96,11 +96,11 @@ func bindNames(root node) error {
 	if err != nil {
 		return err
 	}
-	return checkRead(scopes, read)
+	return checkEveryNameRead(scopes, read)
 }
 
-// checkRead refuses a binding of scopes that read does not hold.
-func checkRead(scopes []*nameScope, read map[*nameBinding]bool) error {
+// checkEveryNameRead refuses a binding of scopes that nothing reads.
+func checkEveryNameRead(scopes []*nameScope, read map[*nameBinding]bool) error {
 	for _, sc := range scopes {
 		for _, b := range sc.order {
 			if !read[b] {

namefence.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"github.com/larvit/fejkdata/internal/grammar"
+	"github.com/larvit/fejkdata/internal/invariant"
 )
 
 // checkNameReads refuses each binding of t that checkUses refuses, a read of a name inside the
@@ -67,6 +68,9 @@ func rendersInside(nodes []node, t *template) bool {
 // template reaches the binder through fields. Where the spelling would be a CLI argument or tag
 // of one reference alone, that entry point's own refusal then names the bare path.
 func (b *nameBinding) checkUses(uses []nameUse) error {
+	if len(uses) == 0 {
+		panic(invariant.Broken("name %q has no read at link, though its compile found one", b.name))
+	}
 	r := uses[0]
 	if len(uses) > 1 || r.nested {
 		return nil