Update required port connection test

src/hugr/validate.rs

@@ -225,12 +225,16 @@ impl<'a> ValidationContext<'a> {
  let port_kind = optype.port_kind(port).unwrap();
  let dir = port.direction();
 
- // Input ports and output linear ports must always be connected
  let mut links = self.hugr.graph.port_links(port_index).peekable();
  let must_be_connected = match dir {
+ // Incoming ports must be connected, except for state order ports, branch case nodes,
+ // and CFG nodes.
  Direction::Incoming => {
- port_kind.is_linear() || matches!(port_kind, EdgeKind::Static(_))
+ port_kind != EdgeKind::StateOrder
+ && port_kind != EdgeKind::ControlFlow
+ && optype.tag() != OpTag::Case
  }
+ // Linear dataflow values must be connected.
  Direction::Outgoing => port_kind.is_linear(),
  };
  if must_be_connected && links.peek().is_none() {