From a1ffe6f22f223953cbf72518af6c7468c768723b Mon Sep 17 00:00:00 2001
From: Douglas Wilson <douglas.wilson@quantinuum.com>
Date: Thu, 13 Mar 2025 14:16:29 +0000
Subject: [PATCH 1/2] test: Failing testcase for #1974

---
 hugr-core/src/hugr/views/sibling_subgraph.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/hugr-core/src/hugr/views/sibling_subgraph.rs b/hugr-core/src/hugr/views/sibling_subgraph.rs
index de3bf22c1a..805ca5cdc4 100644
--- a/hugr-core/src/hugr/views/sibling_subgraph.rs
+++ b/hugr-core/src/hugr/views/sibling_subgraph.rs
@@ -831,6 +831,7 @@ mod tests {
     use cool_asserts::assert_matches;
 
     use crate::builder::inout_sig;
+    use crate::extension::prelude::Noop;
     use crate::hugr::Rewrite;
     use crate::ops::Const;
     use crate::std_extensions::arithmetic::float_types::{self, ConstF64};
@@ -1239,4 +1240,23 @@ mod tests {
         let rep = subg.create_simple_replacement(&h, replacement).unwrap();
         rep.apply(&mut h).unwrap();
     }
+
+    #[test]
+    #[should_panic]
+    fn order_edge() {
+        let (hugr, nop) = {
+            let mut b = DFGBuilder::new(
+                Signature::new_endo(Type::UNIT).with_prelude()
+            ).unwrap();
+            let input = b.input();
+            let nop = b.add_dataflow_op(Noop(Type::UNIT), [input.out_wire(0)]).unwrap();
+            let output = b.output();
+            b.add_other_wire(input.node(), nop.node());
+            b.add_other_wire(nop.node(), output.node());
+            (b.finish_hugr_with_outputs([nop.out_wire(0)]).unwrap(), nop.node())
+        };
+
+        let view = SiblingSubgraph::from_node(nop, &hugr);
+        assert_eq!(view.signature(&hugr), Signature::new_endo(Type::UNIT).with_prelude());
+    }
 }

From 29ca080483e1492c7a86a664472a3415a60dd1a2 Mon Sep 17 00:00:00 2001
From: Seyon Sivarajah <seyon.sivarajah@quantinuum.com>
Date: Thu, 13 Mar 2025 17:13:50 +0000
Subject: [PATCH 2/2] fix: only allow value edges on SiblingSubgraph::from_node

---
 hugr-core/src/hugr/views/sibling_subgraph.rs | 47 +++++++++++---------
 1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/hugr-core/src/hugr/views/sibling_subgraph.rs b/hugr-core/src/hugr/views/sibling_subgraph.rs
index 805ca5cdc4..3bd2ae048f 100644
--- a/hugr-core/src/hugr/views/sibling_subgraph.rs
+++ b/hugr-core/src/hugr/views/sibling_subgraph.rs
@@ -276,25 +276,24 @@ impl<N: HugrNode> SiblingSubgraph<N> {
     ///
     /// The subgraph signature will be given by signature of the node.
     pub fn from_node(node: N, hugr: &impl HugrView<Node = N>) -> Self {
+        let is_value_port = |p: Port| -> bool {
+            hugr.get_optype(node)
+                .port_kind(p)
+                .is_some_and(|k| k.is_value())
+        };
+
         let nodes = vec![node];
         let inputs = hugr
             .node_inputs(node)
-            .filter(|&p| hugr.is_linked(node, p))
-            .map(|p| vec![(node, p)])
+            // accept linked value inputs
+            .filter_map(|p| {
+                (hugr.is_linked(node, p) && is_value_port(p.into())).then_some(vec![(node, p)])
+            })
             .collect_vec();
         let outputs = hugr
             .node_outputs(node)
-            .filter_map(|p| {
-                // accept linked outputs or unlinked value outputs
-                {
-                    hugr.is_linked(node, p)
-                        || hugr
-                            .get_optype(node)
-                            .port_kind(p)
-                            .is_some_and(|k| k.is_value())
-                }
-                .then_some((node, p))
-            })
+            // accept linked or unlinked value outputs
+            .filter_map(|p| is_value_port(p.into()).then_some((node, p)))
             .collect_vec();
 
         Self {
@@ -1242,21 +1241,27 @@ mod tests {
     }
 
     #[test]
-    #[should_panic]
+    // #[should_panic]
     fn order_edge() {
         let (hugr, nop) = {
-            let mut b = DFGBuilder::new(
-                Signature::new_endo(Type::UNIT).with_prelude()
-            ).unwrap();
+            let mut b = DFGBuilder::new(Signature::new_endo(Type::UNIT).with_prelude()).unwrap();
             let input = b.input();
-            let nop = b.add_dataflow_op(Noop(Type::UNIT), [input.out_wire(0)]).unwrap();
+            let nop = b
+                .add_dataflow_op(Noop(Type::UNIT), [input.out_wire(0)])
+                .unwrap();
             let output = b.output();
             b.add_other_wire(input.node(), nop.node());
             b.add_other_wire(nop.node(), output.node());
-            (b.finish_hugr_with_outputs([nop.out_wire(0)]).unwrap(), nop.node())
+            (
+                b.finish_hugr_with_outputs([nop.out_wire(0)]).unwrap(),
+                nop.node(),
+            )
         };
-
+        println!("{}", hugr.mermaid_string());
         let view = SiblingSubgraph::from_node(nop, &hugr);
-        assert_eq!(view.signature(&hugr), Signature::new_endo(Type::UNIT).with_prelude());
+        assert_eq!(
+            view.signature(&hugr),
+            Signature::new_endo(Type::UNIT).with_prelude()
+        );
     }
 }