Name the pin set's inline array and entered's flag apart from pins, and file the draw half of the pin model as its own item

doc_test.go

@@ -95,7 +95,7 @@ func vocabulary(t *testing.T, files []*ast.File) string {
 }
 
 // declaredSymbols is every name the package declares at the top level, a method and
-// a struct field keyed under its type: hold.pin, tableRead.whole.
+// a struct field keyed under its type: pinSet.pin, tableRead.whole.
 func declaredSymbols(files []*ast.File) map[string]bool {
 	names := declaredFuncs(files)
 	for _, f := range files {

drawfence.go

@@ -229,7 +229,7 @@ func (w *drawWalk) walk(n node, at drawAt) {
 	}
 	for _, e := range renderEdges(n) {
 		if cell, isCell := e.to.(*template); isCell && cell.cellOf != nil {
-			if at.alt.excludes(cell) {
+			if at.alt.clash(cell.cellOf, cell.cellRow) != nil {
 				continue
 			}
 			in := at

pins.go

@@ -16,14 +16,14 @@ type tablePin struct {
 // pinSet is the rows of tables fixed so far: by a render, by a path read replayed at load, and by
 // a fence walk over the rows a render can enter, which also holds a row rendered whole, alone.
 type pinSet struct {
-	pins  [8]tablePin // inline, so a render over a country's five-deep geo tree stays off the heap
+	inline [8]tablePin // sized so a render over a country's five-deep geo tree stays off the heap
-	n     int
+	n      int
-	spill map[*table]int
+	spill  map[*table]int
 }
 
 // pinned is the row pinned for t, if any.
 func (p *pinSet) pinned(t *table) (int, bool) {
-	for _, q := range p.pins[:p.n] {
+	for _, q := range p.inline[:p.n] {
 		if q.t == t {
 			return q.row, true
 		}
@@ -43,8 +43,8 @@ func (p *pinSet) mustRow(t *table) int {
 
 // add pins row r of t alone.
 func (p *pinSet) add(t *table, r int) {
-	if p.n < len(p.pins) {
+	if p.n < len(p.inline) {
-		p.pins[p.n] = tablePin{t, r}
+		p.inline[p.n] = tablePin{t, r}
 		p.n++
 		return
 	}
@@ -70,7 +70,7 @@ func (p *pinSet) pin(t *table, r int) {
 
 // each calls fn for every pinned row, in pin order, the spilled ones by table name.
 func (p *pinSet) each(fn func(t *table, r int)) {
-	for _, q := range p.pins[:p.n] {
+	for _, q := range p.inline[:p.n] {
 		fn(q.t, q.row)
 	}
 	spilled := make([]*table, 0, len(p.spill))
@@ -171,10 +171,10 @@ func (p pinSet) clone() pinSet {
 
 // entered is p with row r of t: pinned where the render pins it, alone where the render draws it
 // to render whole. p is left as it was, since a fence walk branches.
-func (p pinSet) entered(t *table, r int, pins bool) pinSet {
+func (p pinSet) entered(t *table, r int, pinsAncestors bool) pinSet {
 	p = p.clone()
 	switch _, in := p.pinned(t); {
-	case pins:
+	case pinsAncestors:
 		p.pin(t, r)
 	case !in:
 		p.add(t, r)
@@ -182,9 +182,6 @@ func (p pinSet) entered(t *table, r int, pins bool) pinSet {
 	return p
 }
 
-// excludes reports whether a cell's row cannot render with the rows pinned.
-func (p *pinSet) excludes(cell *template) bool { return p.clash(cell.cellOf, cell.cellRow) != nil }
-
 // key spells the set for a map, by the tables' identities in path order.
 func (p *pinSet) key() string {
 	var pins []tablePin

todo.md

@@ -43,10 +43,14 @@ This round, in order:
   decided by `indexOutside(body, '(')` in two of them and by `funcCall` in the rest.
 - Name `pathWalk`'s modes: render, probe, check and cover are chosen today by which
   callbacks are nil and whether its session is, and `walkChoice` returns `nil, nil` where
-  none is set. Have the check mode report the tables a read draws, so `tableRead.drawn`
+  none is set. The mode may live in `pathWalk`; the session may not, since beside `pins`
-  and `entered`'s `pins` flag come from the walk rather than a second copy of
+  it moves the hold maps to the heap.
-  `walkTable`'s draw condition and `rowOf`'s ancestor rule. The mode may live in `pathWalk`; the session may not, since beside `pins` it
+- Have the check mode report the tables a read draws, so `tableRead.drawn` and
-  moves the hold maps to the heap.
+  `entered`'s `pinsAncestors` flag stop restating `walkTable`'s draw condition and
+  `rowOf`'s ancestor rule: a change to how a render draws rows still leaves the fence
+  proving the old rule. Hold a row rendered whole in `drawAt` beside `drawn`, so
+  `pinSet` holds only what `pin` pins and `alternatives` needs no exception. Needs the
+  item above.
 - Register a transform once: `transforms` restates the `lowercase`, `uppercase` and
   `ascii` entries in `builtins`, and `valueProof.template` classifies by the first while
   render calls the second. Derive the numeric builtins `valueProof.template` lists in