From 6cb2d143d67f4d2750eef62f96ffb6377fbc3761 Mon Sep 17 00:00:00 2001
From: Lilleman auf Larv <lilleman@larvit.se>
Date: Tue, 29 Sep 2026 13:09:19 +0200
Subject: [PATCH] Refuse own-family reads before any survey, and panic on a
 clash where readSurvey.edge enters a read's pins

---
 data.go       |  3 +++
 drawfence.go  | 10 +++++++++-
 readsurvey.go |  7 ++++++-
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/data.go b/data.go
index c3fd37a..6c1b81b 100644
--- a/data.go
+++ b/data.go
@@ -257,6 +257,9 @@ func checkNodeFences(s nodeScope) error {
 		return err
 	}
 	if refs {
+		if err := s(checkOwnFamilies); err != nil {
+			return err
+		}
 		if err := s(fence.checkDraws); err != nil {
 			return err
 		}
diff --git a/drawfence.go b/drawfence.go
index 8f46f5d..8caffb7 100644
--- a/drawfence.go
+++ b/drawfence.go
@@ -24,7 +24,7 @@ func (f *drawFence) checkDrawGroup(path string, n node) error {
 	return nil
 }
 
-func (f *drawFence) checkDraws(path string, n node) error {
+func checkOwnFamilies(path string, n node) error {
 	t, ok := n.(*template)
 	if !ok {
 		return nil
@@ -32,6 +32,14 @@ func (f *drawFence) checkDraws(path string, n node) error {
 	if err := checkOwnFamily(t); err != nil {
 		return fmt.Errorf("%s: %w", path, err)
 	}
+	return nil
+}
+
+func (f *drawFence) checkDraws(path string, n node) error {
+	t, ok := n.(*template)
+	if !ok {
+		return nil
+	}
 	if !f.readsPath(t) {
 		return nil
 	}
diff --git a/readsurvey.go b/readsurvey.go
index 531e8c7..e77903c 100644
--- a/readsurvey.go
+++ b/readsurvey.go
@@ -122,7 +122,12 @@ func (s *readSurvey) edge(from node, e renderEdge, at surveyAt) {
 			s.reads = append(s.reads, pathRead{at, a, tr})
 		}
 		if tr != nil {
-			tr.pins.each(func(t *table, r int) { at.pins = at.pins.entered(t, r) })
+			tr.pins.each(func(t *table, r int) {
+				if c := at.pins.clash(t, r); c != nil {
+					panic(internalError("%s reads %s past a pinned row of %s, which checkOwnFamily refuses", e.reached(), t.selectorSpelling(r), c.path))
+				}
+				at.pins = at.pins.entered(t, r)
+			})
 		}
 	}
 	s.walk(e.to, at)