Answer architecture round 2: a keyed walk position, a plainer Above test, and docs naming the owner and the key-name refusal

docs/decisions.md

@@ -839,7 +839,7 @@ each value one writer would spread that knot across packages, behind forwarding
 every public method. The draw state, the grammar, `DataType`, what a proof knows of a
 value, the builtins, the reading of data files and a table's rows read no engine type, so
 each sits in a package under `internal/`, behind the import list `imports_test.go` checks.
-A table's rows reach the engine table owning them as a payload of a type parameter. Valid
+A table's rows reach the engine table owning them as their owner, a value of a type parameter. Valid
 until `todo.md` item 107 moves the engine.
 
 ## Goal 5.1's `{…}` covers `{{`, `}}` and a lone `}`, so the goal names no escape

internal/rows/rows.go

@@ -141,8 +141,8 @@ func (t *Table[O]) appendRow(row string, line int) error {
 	return nil
 }
 
-// bindOptions resolves each option to its column and proves what it claims of the
+// bindOptions resolves each option to its column, refuses a name reading the key column, and
-// cells: a key is unique, a weight a positive number.
+// proves what the options claim of the cells: a key is unique, a weight a positive number.
 func (t *Table[O]) bindOptions() error {
 	o := t.options
 	if o.Key != "" && o.Key == o.Name {

internal/rows/rows_test.go

@@ -110,7 +110,7 @@ func TestDrawInDrawsInsideThePinnedParentAndPinsItsAncestors(t *testing.T) {
 		if pr := q.MustRow(country); country.Cell(pr, 0) != city.Cell(r, 0) {
 			t.Fatalf("DrawIn pinned country %s above a city of %s", country.Cell(pr, 0), city.Cell(r, 0))
 		}
-		if above := q.Above(country); func() bool { _, ok := above.Pinned(city); return ok }() {
+		if _, ok := q.Above(country).Pinned(city); ok {
 			t.Fatal("Above(country) kept the city's pin")
 		}
 	}

path.go

@@ -164,7 +164,7 @@ func takeStep(at *pathPos, whole []string, level string, steps []pathStep, pins
 		if err != nil {
 			return steps, err
 		}
-		*at = pathPos{r.next, r.rest, r.descends}
+		*at = pathPos{n: r.next, tail: r.rest, descended: r.descends}
 		return routeSteps(steps, pins, x, r, i)
 	case *template:
 		if x.repeat > 1 && !grammar.IsSelector(at.tail[0]) {