Split drawCheck.reads's condition into readsOnEdge and walksInto, and drop the done item

drawfence.go

@@ -119,7 +119,7 @@ func (c *drawCheck) reads(n node, stopAtGroup bool) bool {
 	}
 	r := false
 	for _, e := range renderEdges(n) {
-		if a, isRef := refRead(n, e.label); (isRef && (len(a.tail) > 0 || readsTable(n, a))) || (!repeats(e.to) && !(stopAtGroup && grouped(e.to)) && c.reads(e.to, stopAtGroup)) {
+		if readsOnEdge(n, e.label) || (walksInto(e.to, stopAtGroup) && c.reads(e.to, stopAtGroup)) {
 			r = true
 			break
 		}
@@ -131,6 +131,19 @@ func (c *drawCheck) reads(n node, stopAtGroup bool) bool {
 	return r
 }
 
+// readsOnEdge reports whether an edge of n is itself a reference path: a reference with a tail, or
+// one naming a table.
+func readsOnEdge(n node, label string) bool {
+	a, isRef := refRead(n, label)
+	return isRef && (len(a.tail) > 0 || readsTable(n, a))
+}
+
+// walksInto reports whether reads walks on into to, which it does short of a repeat, and of a draw
+// group when stopAtGroup.
+func walksInto(to node, stopAtGroup bool) bool {
+	return !repeats(to) && !(stopAtGroup && grouped(to))
+}
+
 func repeats(n node) bool {
 	t, isTemplate := n.(*template)
 	return isTemplate && t.repeat > 1

todo.md

@@ -19,7 +19,6 @@ Self-sufficiency 5.6), every seat capped by Locality or Self-sufficiency.
 
 This round, in order:
 
-- Split `drawCheck.reads`'s six-term condition into named predicates.
 - Rename what names two things: `template.go` holds the token grammar while `template`
   is `node.go`'s type and `Template` `inline.go`'s; `kind` `'b'` is a brace body in
   `ftoken` and a builtin in `formatToken` and `op`; `tokens` is a template's parsed format