feat: Mermaid renderer for hugrs (#852)

Adds a `HugrView::mermaid_string` which produces things like
```mermaid
graph LR
    subgraph 0 ["(0) DFG"]
        direction LR
        1["(1) Input"]
        1--0:0-->3
        1--1:1-->3
        2["(2) Output"]
        3["(3) test.quantum.CX"]
        3--0:1-->4
        3--1:0-->4
        3-.2:2.-4
        4["(4) test.quantum.CX"]
        4--0:0-->2
        4--1:1-->2
    end
```
Note that edges in mermaid are unordered, so I had to add the port
indices explicitly.

The new code in `src/hugr/views/render.rs` is just moved from
`src/hugr/views.rs`.

Closes #696 

Requires CQCL/portgraph#125

Cargo.toml

@@ -25,7 +25,7 @@ extension_inference = []
 
 [dependencies]
 thiserror = "1.0.28"
-portgraph = { version = "0.11.0", features = ["serde", "petgraph"] }
+portgraph = { version = "0.12.0", features = ["serde", "petgraph"] }
 regex = "1.9.5"
 cgmath = { version = "0.18.0", features = ["serde"] }
 num-rational = { version = "0.4.1", features = ["serde"] }
@@ -66,5 +66,5 @@ name = "bench_main"
 harness = false
 
 
-[profile.dev.package]
-insta.opt-level = 3
+[profile.dev.package.insta]
+opt-level = 3

src/builder.rs

@@ -178,8 +178,8 @@ pub(crate) mod test {
 
     use super::handle::BuildHandle;
     use super::{
-        BuildError, Container, DFGBuilder, Dataflow, DataflowHugr, FuncID, FunctionBuilder,
-        ModuleBuilder,
+        BuildError, CFGBuilder, Container, DFGBuilder, Dataflow, DataflowHugr, FuncID,
+        FunctionBuilder, ModuleBuilder,
     };
     use super::{DataflowSubContainer, HugrBuilder};
 
@@ -214,6 +214,14 @@ pub(crate) mod test {
         dfg_builder.finish_prelude_hugr_with_outputs([i1]).unwrap()
     }
 
+    #[fixture]
+    pub(crate) fn simple_cfg_hugr() -> Hugr {
+        let mut cfg_builder =
+            CFGBuilder::new(FunctionType::new(type_row![NAT], type_row![NAT])).unwrap();
+        super::cfg::test::build_basic_cfg(&mut cfg_builder).unwrap();
+        cfg_builder.finish_prelude_hugr().unwrap()
+    }
+
     /// A helper method which creates a DFG rooted hugr with closed resources,
     /// for tests which want to avoid having open extension variables after
     /// inference. Using DFGBuilder will default to a root node with an open

src/builder/cfg.rs

@@ -404,7 +404,7 @@ impl BlockBuilder<Hugr> {
 }
 
 #[cfg(test)]
-mod test {
+pub(crate) mod test {
     use crate::builder::build_traits::HugrBuilder;
     use crate::builder::{DataflowSubContainer, ModuleBuilder};
 
@@ -453,7 +453,7 @@ mod test {
         Ok(())
     }
 
-    fn build_basic_cfg<T: AsMut<Hugr> + AsRef<Hugr>>(
+    pub(crate) fn build_basic_cfg<T: AsMut<Hugr> + AsRef<Hugr>>(
         cfg_builder: &mut CFGBuilder<T>,
     ) -> Result<(), BuildError> {
         let sum2_variants = vec![type_row![NAT], type_row![NAT]];

src/hugr/views.rs

@@ -2,6 +2,7 @@
 
 pub mod descendants;
 pub mod petgraph;
+pub mod render;
 mod root_checked;
 pub mod sibling;
 pub mod sibling_subgraph;
@@ -12,19 +13,20 @@ mod tests;
 use std::iter::Map;
 
 pub use self::petgraph::PetgraphWrapper;
+use self::render::RenderConfig;
 pub use descendants::DescendantsGraph;
 pub use root_checked::RootChecked;
 pub use sibling::SiblingGraph;
 pub use sibling_subgraph::SiblingSubgraph;
 
 use context_iterators::{ContextIterator, IntoContextIterator, MapWithCtx};
 use itertools::{Itertools, MapInto};
-use portgraph::dot::{DotFormat, EdgeStyle, NodeStyle, PortStyle};
+use portgraph::render::{DotFormat, MermaidFormat};
 use portgraph::{multiportgraph, LinkView, MultiPortGraph, PortView};
 
 use super::{Hugr, HugrError, NodeMetadata, NodeMetadataMap, NodeType, DEFAULT_NODETYPE};
 use crate::ops::handle::NodeHandle;
-use crate::ops::{OpName, OpParent, OpTag, OpTrait, OpType};
+use crate::ops::{OpParent, OpTag, OpTrait, OpType};
 
 use crate::types::Type;
 use crate::types::{EdgeKind, FunctionType};
@@ -347,52 +349,61 @@ pub trait HugrView: sealed::HugrInternals {
         PetgraphWrapper { hugr: self }
     }
 
-    /// Return dot string showing underlying graph and hierarchy side by side.
-    fn dot_string(&self) -> String {
+    /// Return the mermaid representation of the underlying hierarchical graph.
+    ///
+    /// The hierarchy is represented using subgraphs. Edges are labelled with
+    /// their source and target ports.
+    ///
+    /// For a more detailed representation, use the [`HugrView::dot_string`]
+    /// format instead.
+    fn mermaid_string(&self) -> String
+    where
+        Self: Sized,
+    {
+        self.mermaid_string_with_config(RenderConfig {
+            node_indices: true,
+            port_offsets_in_edges: true,
+            type_labels_in_edges: true,
+        })
+    }
+
+    /// Return the mermaid representation of the underlying hierarchical graph.
+    ///
+    /// The hierarchy is represented using subgraphs. Edges are labelled with
+    /// their source and target ports.
+    ///
+    /// For a more detailed representation, use the [`HugrView::dot_string`]
+    /// format instead.
+    fn mermaid_string_with_config(&self, config: RenderConfig) -> String
+    where
+        Self: Sized,
+    {
         let hugr = self.base_hugr();
         let graph = self.portgraph();
+        graph
+            .mermaid_format()
+            .with_hierarchy(&hugr.hierarchy)
+            .with_node_style(render::node_style(self, config))
+            .with_edge_style(render::edge_style(self, config))
+            .finish()
+    }
+
+    /// Return the graphviz representation of the underlying graph and hierarchy side by side.
+    ///
+    /// For a simpler representation, use the [`HugrView::mermaid_string`] format instead.
+    fn dot_string(&self) -> String
+    where
+        Self: Sized,
+    {
+        let hugr = self.base_hugr();
+        let graph = self.portgraph();
+        let config = RenderConfig::default();
         graph
             .dot_format()
             .with_hierarchy(&hugr.hierarchy)
-            .with_node_style(|n| {
-                NodeStyle::Box(format!(
-                    "({ni}) {name}",
-                    ni = n.index(),
-                    name = self.get_optype(n.into()).name()
-                ))
-            })
-            .with_port_style(|port| {
-                let node = graph.port_node(port).unwrap();
-                let optype = self.get_optype(node.into());
-                let offset = graph.port_offset(port).unwrap();
-                match optype.port_kind(offset).unwrap() {
-                    EdgeKind::Static(ty) => {
-                        PortStyle::new(html_escape::encode_text(&format!("{}", ty)))
-                    }
-                    EdgeKind::Value(ty) => {
-                        PortStyle::new(html_escape::encode_text(&format!("{}", ty)))
-                    }
-                    EdgeKind::StateOrder => match graph.port_links(port).count() > 0 {
-                        true => PortStyle::text("", false),
-                        false => PortStyle::Hidden,
-                    },
-                    _ => PortStyle::text("", true),
-                }
-            })
-            .with_edge_style(|src, tgt| {
-                let src_node = graph.port_node(src).unwrap();
-                let src_optype = self.get_optype(src_node.into());
-                let src_offset = graph.port_offset(src).unwrap();
-                let tgt_node = graph.port_node(tgt).unwrap();
-
-                if hugr.hierarchy.parent(src_node) != hugr.hierarchy.parent(tgt_node) {
-                    EdgeStyle::Dashed
-                } else if src_optype.port_kind(src_offset) == Some(EdgeKind::StateOrder) {
-                    EdgeStyle::Dotted
-                } else {
-                    EdgeStyle::Solid
-                }
-            })
+            .with_node_style(render::node_style(self, config))
+            .with_port_style(render::port_style(self, config))
+            .with_edge_style(render::edge_style(self, config))
             .finish()
     }
 

src/hugr/views/render.rs

@@ -0,0 +1,120 @@
+//! Helper methods to compute the node/edge/port style when rendering a HUGR
+//! into dot or mermaid format.
+
+use portgraph::render::{EdgeStyle, NodeStyle, PortStyle};
+use portgraph::{LinkView, NodeIndex, PortIndex, PortView};
+
+use crate::ops::OpName;
+use crate::types::EdgeKind;
+use crate::HugrView;
+
+/// Configuration for rendering a HUGR graph.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[non_exhaustive]
+pub struct RenderConfig {
+    /// Show the node index in the graph nodes.
+    pub node_indices: bool,
+    /// Show port offsets in the graph edges.
+    pub port_offsets_in_edges: bool,
+    /// Show type labels on edges.
+    pub type_labels_in_edges: bool,
+}
+
+impl Default for RenderConfig {
+    fn default() -> Self {
+        Self {
+            node_indices: true,
+            port_offsets_in_edges: true,
+            type_labels_in_edges: true,
+        }
+    }
+}
+
+/// Formatter method to compute a node style.
+pub(super) fn node_style<H: HugrView>(
+    h: &H,
+    config: RenderConfig,
+) -> Box<dyn FnMut(NodeIndex) -> NodeStyle + '_> {
+    if config.node_indices {
+        Box::new(move |n| {
+            NodeStyle::Box(format!(
+                "({ni}) {name}",
+                ni = n.index(),
+                name = h.get_optype(n.into()).name()
+            ))
+        })
+    } else {
+        Box::new(move |n| NodeStyle::Box(h.get_optype(n.into()).name().to_string()))
+    }
+}
+
+/// Formatter method to compute a port style.
+pub(super) fn port_style<H: HugrView>(
+    h: &H,
+    _config: RenderConfig,
+) -> Box<dyn FnMut(PortIndex) -> PortStyle + '_> {
+    let graph = h.portgraph();
+    Box::new(move |port| {
+        let node = graph.port_node(port).unwrap();
+        let optype = h.get_optype(node.into());
+        let offset = graph.port_offset(port).unwrap();
+        match optype.port_kind(offset).unwrap() {
+            EdgeKind::Static(ty) => PortStyle::new(html_escape::encode_text(&format!("{}", ty))),
+            EdgeKind::Value(ty) => PortStyle::new(html_escape::encode_text(&format!("{}", ty))),
+            EdgeKind::StateOrder => match graph.port_links(port).count() > 0 {
+                true => PortStyle::text("", false),
+                false => PortStyle::Hidden,
+            },
+            _ => PortStyle::text("", true),
+        }
+    })
+}
+
+/// Formatter method to compute an edge style.
+#[allow(clippy::type_complexity)]
+pub(super) fn edge_style<H: HugrView>(
+    h: &H,
+    config: RenderConfig,
+) -> Box<
+    dyn FnMut(
+            <H::Portgraph<'_> as LinkView>::LinkEndpoint,
+            <H::Portgraph<'_> as LinkView>::LinkEndpoint,
+        ) -> EdgeStyle
+        + '_,
+> {
+    let graph = h.portgraph();
+    Box::new(move |src, tgt| {
+        let src_node = graph.port_node(src).unwrap();
+        let src_optype = h.get_optype(src_node.into());
+        let src_offset = graph.port_offset(src).unwrap();
+        let tgt_offset = graph.port_offset(tgt).unwrap();
+
+        let port_kind = src_optype.port_kind(src_offset).unwrap();
+
+        // StateOrder edges: Dotted line.
+        // Control flow edges: Dashed line.
+        // Static and Value edges: Solid line with label.
+        let style = match port_kind {
+            EdgeKind::StateOrder => EdgeStyle::Dotted,
+            EdgeKind::ControlFlow => EdgeStyle::Dashed,
+            EdgeKind::Static(_) | EdgeKind::Value(_) => EdgeStyle::Solid,
+        };
+
+        // Compute the label for the edge, given the setting flags.
+        //
+        // Only static and value edges have types to display.
+        let label = match (
+            config.port_offsets_in_edges,
+            config.type_labels_in_edges,
+            port_kind,
+        ) {
+            (true, true, EdgeKind::Static(ty) | EdgeKind::Value(ty)) => {
+                format!("{}:{}\n{ty}", src_offset.index(), tgt_offset.index())
+            }
+            (true, _, _) => format!("{}:{}", src_offset.index(), tgt_offset.index()),
+            (false, true, EdgeKind::Static(ty) | EdgeKind::Value(ty)) => format!("{}", ty),
+            _ => return style,
+        };
+        style.with_label(label)
+    })
+}

src/hugr/views/snapshots/hugr__hugr__views__tests__dot_cfg.snap

@@ -0,0 +1,5 @@
+---
+source: src/hugr/views/tests.rs
+expression: h.dot_string()
+---
+"digraph {\n0 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(0) CFG</td></tr></table>>]\n1 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">0</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(1) ExitBlock</td></tr></table>>]\n2 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"2\" cellpadding=\"1\" border=\"0\">0</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"2\">(2) DataflowBlock</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">0</td><td port=\"out1\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">1</td></tr></table>>]\n2:out0 -> 7:in0 [style=\"dashed\"]\n2:out1 -> 1:in0 [style=\"dashed\"]\n3 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(3) Input</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: usize</td></tr></table>>]\n3:out0 -> 5:in0 [style=\"\"]\n4 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum([Tuple([usize]), Tuple([usize])])</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(4) Output</td></tr></table>>]\n5 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: usize</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(5) MakeTuple</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Tuple([usize])</td></tr></table>>]\n5:out0 -> 6:in0 [style=\"\"]\n6 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Tuple([usize])</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(6) Tag</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum([Tuple([usize]), Tuple([usize])])</td></tr></table>>]\n6:out0 -> 4:in0 [style=\"\"]\n7 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">0</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(7) DataflowBlock</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">0</td></tr></table>>]\n7:out0 -> 1:in0 [style=\"dashed\"]\n8 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(8) Input</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: usize</td></tr></table>>]\n8:out0 -> 9:in1 [style=\"\"]\n9 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(1))</td><td port=\"in1\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >1: usize</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"2\">(9) Output</td></tr></table>>]\n10 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(10) const:sum:{tag:0, val:const:seq:{}}</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(1))</td></tr></table>>]\n10:out0 -> 11:in0 [style=\"\"]\n11 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(1))</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(11) LoadConstant</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(1))</td></tr></table>>]\n11:out0 -> 9:in0 [style=\"\"]\nhier0 [shape=plain label=\"0\"]\nhier0 -> hier2  [style = \"dashed\"] \nhier0 -> hier1  [style = \"dashed\"] \nhier0 -> hier7  [style = \"dashed\"] \nhier1 [shape=plain label=\"1\"]\nhier2 [shape=plain label=\"2\"]\nhier2 -> hier3  [style = \"dashed\"] \nhier2 -> hier4  [style = \"dashed\"] \nhier2 -> hier5  [style = \"dashed\"] \nhier2 -> hier6  [style = \"dashed\"] \nhier3 [shape=plain label=\"3\"]\nhier4 [shape=plain label=\"4\"]\nhier5 [shape=plain label=\"5\"]\nhier6 [shape=plain label=\"6\"]\nhier7 [shape=plain label=\"7\"]\nhier7 -> hier8  [style = \"dashed\"] \nhier7 -> hier9  [style = \"dashed\"] \nhier7 -> hier10  [style = \"dashed\"] \nhier7 -> hier11  [style = \"dashed\"] \nhier8 [shape=plain label=\"8\"]\nhier9 [shape=plain label=\"9\"]\nhier10 [shape=plain label=\"10\"]\nhier11 [shape=plain label=\"11\"]\n}\n"

src/hugr/views/snapshots/hugr__hugr__views__tests__dot_string.snap → src/hugr/views/snapshots/hugr__hugr__views__tests__dot_dfg.snap

@@ -3,4 +3,3 @@ source: src/hugr/views/tests.rs
 expression: h.dot_string()
 ---
 "digraph {\n0 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(0) DFG</td></tr></table>>]\n1 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"2\">(1) Input</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: qubit</td><td port=\"out1\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >1: qubit</td></tr></table>>]\n1:out0 -> 3:in0 [style=\"\"]\n1:out1 -> 3:in1 [style=\"\"]\n2 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: qubit</td><td port=\"in1\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >1: qubit</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"2\">(2) Output</td></tr></table>>]\n3 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"3\" cellpadding=\"1\" >0: qubit</td><td port=\"in1\" align=\"text\" colspan=\"3\" cellpadding=\"1\" >1: qubit</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"6\">(3) test.quantum.CX</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"2\" cellpadding=\"1\" >0: qubit</td><td port=\"out1\" align=\"text\" colspan=\"2\" cellpadding=\"1\" >1: qubit</td><td port=\"out2\" align=\"text\" colspan=\"2\" cellpadding=\"1\" border=\"0\"></td></tr></table>>]\n3:out0 -> 4:in1 [style=\"\"]\n3:out1 -> 4:in0 [style=\"\"]\n3:out2 -> 4:in2 [style=\"dotted\"]\n4 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"2\" cellpadding=\"1\" >0: qubit</td><td port=\"in1\" align=\"text\" colspan=\"2\" cellpadding=\"1\" >1: qubit</td><td port=\"in2\" align=\"text\" colspan=\"2\" cellpadding=\"1\" border=\"0\"></td></tr><tr><td align=\"text\" border=\"0\" colspan=\"6\">(4) test.quantum.CX</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"3\" cellpadding=\"1\" >0: qubit</td><td port=\"out1\" align=\"text\" colspan=\"3\" cellpadding=\"1\" >1: qubit</td></tr></table>>]\n4:out0 -> 2:in0 [style=\"\"]\n4:out1 -> 2:in1 [style=\"\"]\nhier0 [shape=plain label=\"0\"]\nhier0 -> hier1  [style = \"dashed\"] \nhier0 -> hier2  [style = \"dashed\"] \nhier0 -> hier3  [style = \"dashed\"] \nhier0 -> hier4  [style = \"dashed\"] \nhier1 [shape=plain label=\"1\"]\nhier2 [shape=plain label=\"2\"]\nhier3 [shape=plain label=\"3\"]\nhier4 [shape=plain label=\"4\"]\n}\n"
-

src/hugr/views/snapshots/hugr__hugr__views__tests__dot_empty_dfg.snap

@@ -0,0 +1,5 @@
+---
+source: src/hugr/views/tests.rs
+expression: h.dot_string()
+---
+"digraph {\n0 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(0) DFG</td></tr></table>>]\n1 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(1) Input</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(2))</td></tr></table>>]\n1:out0 -> 2:in0 [style=\"\"]\n2 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(2))</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(2) Output</td></tr></table>>]\nhier0 [shape=plain label=\"0\"]\nhier0 -> hier1  [style = \"dashed\"] \nhier0 -> hier2  [style = \"dashed\"] \nhier1 [shape=plain label=\"1\"]\nhier2 [shape=plain label=\"2\"]\n}\n"

src/hugr/views/snapshots/hugr__hugr__views__tests__mmd_cfg.snap

@@ -0,0 +1,32 @@
+---
+source: src/hugr/views/tests.rs
+expression: h.mermaid_string()
+---
+graph LR
+    subgraph 0 ["(0) CFG"]
+        direction LR
+        subgraph 2 ["(2) DataflowBlock"]
+            direction LR
+            3["(3) Input"]
+            3--"0:0<br>usize"-->5
+            4["(4) Output"]
+            5["(5) MakeTuple"]
+            5--"0:0<br>Tuple([usize])"-->6
+            6["(6) Tag"]
+            6--"0:0<br>Sum([Tuple([usize]), Tuple([usize])])"-->4
+        end
+        2-."0:0".->7
+        2-."1:0".->1
+        1["(1) ExitBlock"]
+        subgraph 7 ["(7) DataflowBlock"]
+            direction LR
+            8["(8) Input"]
+            8--"0:1<br>usize"-->9
+            9["(9) Output"]
+            10["(10) const:sum:{tag:0, val:const:seq:{}}"]
+            10--"0:0<br>Sum(UnitSum(1))"-->11
+            11["(11) LoadConstant"]
+            11--"0:0<br>Sum(UnitSum(1))"-->9
+        end
+        7-."0:0".->1
+    end