feat!: Remove RootCheckable (#2704)

Closes #2577 .

BREAKING CHANGE: Use `RootChecked` or `HugrView` instead of
`RootCheckable`.

Author: cqc-alec

hugr-core/src/hugr/views.rs

@@ -19,7 +19,7 @@ pub use self::petgraph::PetgraphWrapper;
 use self::render::{MermaidFormatter, RenderConfig};
 pub use nodes_iter::NodesIter;
 pub use rerooted::Rerooted;
-pub use root_checked::{InvalidSignature, RootCheckable, RootChecked, check_tag};
+pub use root_checked::{InvalidSignature, RootChecked, check_tag};
 pub use sibling_subgraph::SiblingSubgraph;
 
 use itertools::Itertools;

hugr-core/src/hugr/views/root_checked.rs

@@ -67,26 +67,6 @@ impl<H: AsRef<Hugr>, Handle> AsRef<Hugr> for RootChecked<H, Handle> {
     }
 }
 
-/// A trait for types that can be checked for a specific [`OpTag`] at their entrypoint node.
-///
-/// This is used mainly specifying function inputs that may either be a [`HugrView`] or an already checked [`RootChecked`].
-pub trait RootCheckable<H: HugrView, Handle: NodeHandle<H::Node>>: Sized {
-    /// Wrap the Hugr in a [`RootChecked`] if it is valid for the required [`OpTag`].
-    ///
-    /// If `Self` is already a [`RootChecked`], it is a no-op.
-    fn try_into_checked(self) -> Result<RootChecked<H, Handle>, HugrError>;
-}
-impl<H: HugrView, Handle: NodeHandle<H::Node>> RootCheckable<H, Handle> for H {
-    fn try_into_checked(self) -> Result<RootChecked<H, Handle>, HugrError> {
-        RootChecked::try_new(self)
-    }
-}
-impl<H: HugrView, Handle: NodeHandle<H::Node>> RootCheckable<H, Handle> for RootChecked<H, Handle> {
-    fn try_into_checked(self) -> Result<RootChecked<H, Handle>, HugrError> {
-        Ok(self)
-    }
-}
-
 /// Check that the node in a HUGR can be represented by the required tag.
 pub fn check_tag<Required: NodeHandle<N>, N>(
     hugr: &impl HugrView<Node = N>,

hugr-core/src/hugr/views/sibling_subgraph.rs

@@ -27,7 +27,7 @@ use crate::ops::{NamedOp, OpTag, OpTrait, OpType};
 use crate::types::{Signature, Type};
 use crate::{Hugr, IncomingPort, Node, OutgoingPort, Port, SimpleReplacement};
 
-use super::root_checked::RootCheckable;
+use super::RootChecked;
 
 /// A non-empty convex subgraph of a HUGR sibling graph.
 ///
@@ -110,15 +110,12 @@ impl<N: HugrNode> SiblingSubgraph<N> {
     /// This will return an [`InvalidSubgraph::EmptySubgraph`] error if the
     /// subgraph is empty.
     pub fn try_new_dataflow_subgraph<'h, H, Root>(
-        dfg_graph: impl RootCheckable<&'h H, Root>,
+        dfg_graph: RootChecked<&'h H, Root>,
     ) -> Result<Self, InvalidSubgraph<N>>
     where
         H: 'h + Clone + HugrView<Node = N>,
         Root: ContainerHandle<N, ChildrenHandle = DataflowOpID>,
     {
-        let Ok(dfg_graph) = dfg_graph.try_into_checked() else {
-            return Err(InvalidSubgraph::NonDataflowRegion);
-        };
         let dfg_graph = dfg_graph.into_hugr();
 
         let parent = HugrView::entrypoint(&dfg_graph);
@@ -1651,7 +1648,9 @@ mod tests {
     fn construct_simple_replacement() -> Result<(), InvalidSubgraph> {
         let (mut hugr, func_root) = build_hugr().unwrap();
         let func = hugr.with_entrypoint(func_root);
-        let sub = SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(&func)?;
+        let sub = SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(
+            RootChecked::try_new(&func).expect("Root should be FuncDefn."),
+        )?;
         assert!(sub.validate(&func, Default::default()).is_ok());
 
         let empty_dfg = {
@@ -1699,7 +1698,9 @@ mod tests {
     fn test_signature() -> Result<(), InvalidSubgraph> {
         let (hugr, dfg) = build_hugr().unwrap();
         let func = hugr.with_entrypoint(dfg);
-        let sub = SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(&func)?;
+        let sub = SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(
+            RootChecked::try_new(&func).expect("Root should be FuncDefn."),
+        )?;
         assert!(sub.validate(&func, Default::default()).is_ok());
         assert_eq!(
             sub.signature(&func),
@@ -1732,10 +1733,12 @@ mod tests {
         let (hugr, func_root) = build_hugr().unwrap();
         let func = hugr.with_entrypoint(func_root);
         assert_eq!(
-            SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(&func)
-                .unwrap()
-                .nodes()
-                .len(),
+            SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(
+                RootChecked::try_new(&func).expect("Root should be FuncDefn.")
+            )
+            .unwrap()
+            .nodes()
+            .len(),
             4
         );
     }
@@ -1848,8 +1851,10 @@ mod tests {
     fn preserve_signature() {
         let (hugr, func_root) = build_hugr_classical().unwrap();
         let func_graph = hugr.with_entrypoint(func_root);
-        let func =
-            SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(&func_graph).unwrap();
+        let func = SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(
+            RootChecked::try_new(&func_graph).expect("Root should be FuncDefn."),
+        )
+        .unwrap();
         let func_defn = hugr.get_optype(func_root).as_func_defn().unwrap();
         assert_eq!(func_defn.signature(), &func.signature(&func_graph).into());
     }
@@ -1858,8 +1863,10 @@ mod tests {
     fn extract_subgraph() {
         let (hugr, func_root) = build_hugr().unwrap();
         let func_graph = hugr.with_entrypoint(func_root);
-        let subgraph =
-            SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(&func_graph).unwrap();
+        let subgraph = SiblingSubgraph::try_new_dataflow_subgraph::<_, FuncID<true>>(
+            RootChecked::try_new(&func_graph).expect("Root should be FuncDefn."),
+        )
+        .unwrap();
         let extracted = subgraph.extract_subgraph(&hugr, "region");
 
         extracted.validate().unwrap();
@@ -1883,7 +1890,10 @@ mod tests {
             .outputs();
         let outw = [outw1].into_iter().chain(outw2);
         let h = builder.finish_hugr_with_outputs(outw).unwrap();
-        let subg = SiblingSubgraph::try_new_dataflow_subgraph::<_, DfgID>(&h).unwrap();
+        let subg = SiblingSubgraph::try_new_dataflow_subgraph::<_, DfgID>(
+            RootChecked::try_new(&h).expect("Root should be DFG."),
+        )
+        .unwrap();
         assert_eq!(subg.nodes().len(), 2);
     }
 
@@ -2178,9 +2188,10 @@ mod tests {
 
     #[rstest]
     fn test_call_subgraph_from_dfg(hugr_call_subgraph: Hugr) {
-        let subg =
-            SiblingSubgraph::try_new_dataflow_subgraph::<_, DataflowParentID>(&hugr_call_subgraph)
-                .unwrap();
+        let subg = SiblingSubgraph::try_new_dataflow_subgraph::<_, DataflowParentID>(
+            RootChecked::try_new(&hugr_call_subgraph).expect("Root should be DFG container."),
+        )
+        .unwrap();
 
         assert_eq!(subg.function_calls.len(), 1);
         assert_eq!(subg.function_calls[0].len(), 2);

hugr-passes/src/half_node.rs

@@ -3,7 +3,7 @@ use std::hash::Hash;
 use super::nest_cfgs::CfgNodeMap;
 
 use hugr_core::hugr::internal::HugrInternals;
-use hugr_core::hugr::views::RootCheckable;
+use hugr_core::hugr::views::RootChecked;
 use hugr_core::ops::handle::CfgID;
 use hugr_core::ops::{OpTag, OpTrait};
 use hugr_core::{Direction, HugrView, Node};
@@ -32,9 +32,8 @@ struct HalfNodeView<H: HugrInternals> {
 
 impl<H: HugrView> HalfNodeView<H> {
     #[allow(unused)]
-    pub(crate) fn new(h: impl RootCheckable<H, CfgID<H::Node>>) -> Self {
-        let checked = h.try_into_checked().expect("Hugr must be a CFG region");
-        let h = checked.into_hugr();
+    pub(crate) fn new(h: RootChecked<H, CfgID<H::Node>>) -> Self {
+        let h = h.into_hugr();
 
         let (entry, exit) = {
             let mut children = h.children(h.entrypoint());
@@ -99,6 +98,7 @@ mod test {
     use super::super::nest_cfgs::{EdgeClassifier, test::*};
     use super::{HalfNode, HalfNodeView};
     use hugr_core::builder::BuildError;
+    use hugr_core::hugr::views::RootChecked;
     use hugr_core::ops::handle::NodeHandle;
 
     use itertools::Itertools;
@@ -118,7 +118,7 @@ mod test {
         //               \---<---<---<---<---<---<---<---<---<---/
         // Allowing to identify two nested regions (and fixing the problem with an IdentityCfgMap on the same example)
 
-        let v = HalfNodeView::new(&h);
+        let v = HalfNodeView::new(RootChecked::try_new(&h).expect("Root should be CFG."));
 
         let edge_classes = EdgeClassifier::get_edge_classes(&v);
         let HalfNodeView { h: _, entry, exit } = v;

hugr-passes/src/lib.rs

@@ -25,7 +25,7 @@ pub mod untuple;
 /// Merge basic blocks. Subset of [normalize_cfgs], use the latter.
 #[deprecated(note = "Use normalize_cfgs", since = "0.23.0")]
 pub mod merge_bbs {
-    use hugr_core::hugr::{hugrmut::HugrMut, views::RootCheckable};
+    use hugr_core::hugr::{hugrmut::HugrMut, views::RootChecked};
     use hugr_core::ops::handle::CfgID;
 
     /// Merge any basic blocks that are direct children of the specified CFG
@@ -38,11 +38,8 @@ pub mod merge_bbs {
     ///
     /// [OpType::CFG]: hugr_core::ops::OpType::CFG
     #[deprecated(note = "Use version in normalize_cfgs", since = "0.23.0")]
-    pub fn merge_basic_blocks<'h, H: 'h + HugrMut>(
-        cfg: impl RootCheckable<&'h mut H, CfgID<H::Node>>,
-    ) {
-        let checked = cfg.try_into_checked().expect("Hugr must be a CFG region");
-        super::normalize_cfgs::merge_basic_blocks(checked.into_hugr()).unwrap();
+    pub fn merge_basic_blocks<'h, H: 'h + HugrMut>(cfg: RootChecked<&'h mut H, CfgID<H::Node>>) {
+        super::normalize_cfgs::merge_basic_blocks(cfg.into_hugr()).unwrap();
     }
 }
 

hugr-passes/src/nest_cfgs.rs

@@ -45,11 +45,10 @@ use itertools::Itertools;
 use thiserror::Error;
 
 use hugr_core::hugr::patch::outline_cfg::OutlineCfg;
-use hugr_core::hugr::views::{HugrView, RootCheckable};
+use hugr_core::hugr::views::HugrView;
 use hugr_core::hugr::{Patch, hugrmut::HugrMut};
 use hugr_core::ops::OpTag;
 use hugr_core::ops::OpTrait;
-use hugr_core::ops::handle::CfgID;
 use hugr_core::{Direction, Hugr, Node};
 
 /// A "view" of a CFG in a Hugr which allows basic blocks in the underlying CFG to be split into
@@ -220,10 +219,7 @@ pub struct IdentityCfgMap<H: HugrView> {
 }
 impl<H: HugrView> IdentityCfgMap<H> {
     /// Creates an [`IdentityCfgMap`] for the specified CFG
-    pub fn new(h: impl RootCheckable<H, CfgID<H::Node>>) -> Self {
-        let h = h.try_into_checked().expect("Hugr must be a CFG region");
-        let h = h.into_hugr();
-
+    pub fn new(h: H) -> Self {
         // Panic if malformed enough not to have two children
         let (entry, exit) = h.children(h.entrypoint()).take(2).collect_tuple().unwrap();
         debug_assert_eq!(h.get_optype(exit).tag(), OpTag::BasicBlockExit);
@@ -582,7 +578,6 @@ pub(crate) mod test {
 
     use hugr_core::Node;
     use hugr_core::hugr::patch::insert_identity::{IdentityInsertion, IdentityInsertionError};
-    use hugr_core::hugr::views::RootChecked;
     use hugr_core::ops::Value;
     use hugr_core::ops::handle::{BasicBlockID, ConstID, NodeHandle};
     use hugr_core::types::{EdgeKind, Signature};
@@ -632,11 +627,11 @@ pub(crate) mod test {
         let exit = cfg_builder.exit_block();
         cfg_builder.branch(&tail, 0, &exit)?;
 
-        let mut h = cfg_builder.finish_hugr()?;
-        let rc = RootChecked::<_, CfgID>::try_new(&mut h).unwrap();
+        let h = cfg_builder.finish_hugr()?;
         let (entry, exit) = (entry.node(), exit.node());
         let (split, merge, head, tail) = (split.node(), merge.node(), head.node(), tail.node());
-        let edge_classes = EdgeClassifier::get_edge_classes(&IdentityCfgMap::new(rc.as_ref()));
+        let mut v = IdentityCfgMap::new(h);
+        let edge_classes = EdgeClassifier::get_edge_classes(&v);
         let [&left, &right] = edge_classes
             .keys()
             .filter(|(s, _)| *s == split)
@@ -657,7 +652,8 @@ pub(crate) mod test {
                 sorted([(entry, split), (merge, head), (tail, exit)]), // Two regions, conditional and then loop.
             ])
         );
-        transform_cfg_to_nested(&mut IdentityCfgMap::new(rc));
+        transform_cfg_to_nested(&mut v);
+        let h = v.h;
         h.validate().unwrap();
         assert_eq!(3, depth(&h, entry));
         assert_eq!(3, depth(&h, exit));
@@ -693,7 +689,7 @@ pub(crate) mod test {
             .try_into()
             .unwrap();
 
-        let v = IdentityCfgMap::new(RootChecked::try_new(&h).unwrap());
+        let v = IdentityCfgMap::new(h);
         let edge_classes = EdgeClassifier::get_edge_classes(&v);
         let [&left, &right] = edge_classes
             .keys()
@@ -783,7 +779,7 @@ pub(crate) mod test {
         // Here we would like an indication that we can make two nested regions,
         // but there is no edge to act as entry to a region containing just the conditional :-(.
 
-        let v = IdentityCfgMap::new(RootChecked::try_new(&h).unwrap());
+        let v = IdentityCfgMap::new(h);
         let edge_classes = EdgeClassifier::get_edge_classes(&v);
         let IdentityCfgMap { h: _, entry, exit } = v;
         // merge is unique predecessor of tail

hugr-persistent/src/walker.rs

@@ -62,7 +62,7 @@ use hugr_core::ops::handle::DataflowParentID;
 use itertools::{Either, Itertools};
 use thiserror::Error;
 
-use hugr_core::{Direction, Hugr, HugrView, Port, PortIndex, hugr::views::RootCheckable};
+use hugr_core::{Direction, Hugr, HugrView, Port, PortIndex, hugr::views::RootChecked};
 
 use crate::{Commit, PersistentReplacement, PinnedSubgraph};
 
@@ -302,7 +302,7 @@ impl<'a> Walker<'a> {
     pub fn try_create_commit(
         &self,
         subgraph: impl Into<PinnedSubgraph>,
-        repl: impl RootCheckable<Hugr, DataflowParentID>,
+        mut repl: RootChecked<Hugr, DataflowParentID>,
         map_boundary: impl Fn(PatchNode, Port) -> Port,
     ) -> Result<Commit<'a>, InvalidCommit> {
         let pinned_subgraph = subgraph.into();
@@ -312,7 +312,6 @@ impl<'a> Walker<'a> {
             .map(|id| self.selected_commits.get_commit(id).clone());
 
         let repl = {
-            let mut repl = repl.try_into_checked().expect("replacement is not DFG");
             let new_inputs = subgraph
                 .incoming_ports()
                 .iter()
@@ -783,7 +782,7 @@ mod tests {
         let commit = walker
             .try_create_commit(
                 PinnedSubgraph::try_from_pinned(std::iter::empty(), [wire], &walker).unwrap(),
-                empty_hugr,
+                RootChecked::try_new(empty_hugr).expect("Root should be DFG."),
                 |node, port| {
                     assert_eq!(port.index(), 0);
                     assert!([not0, not2].contains(&node));

hugr-persistent/tests/persistent_walker_example.rs

@@ -8,6 +8,7 @@ use hugr_core::{
     Hugr, HugrView, IncomingPort, OutgoingPort, Port, PortIndex,
     builder::{DFGBuilder, Dataflow, DataflowHugr, endo_sig},
     extension::prelude::qb_t,
+    hugr::views::RootChecked,
     ops::OpType,
     types::EdgeKind,
 };
@@ -251,7 +252,7 @@ fn create_commit<'a>(wire: PersistentWire, walker: &Walker<'a>) -> Option<Commit
             // Create the commit
             walker.try_create_commit(
                 PinnedSubgraph::try_from_wires(wires, walker).unwrap(),
-                empty_2qb_hugr(add_swap),
+                RootChecked::try_new(empty_2qb_hugr(add_swap)).expect("Root should be DFG."),
                 |_, port| {
                     // the incoming/outgoing ports of the subgraph map trivially to the empty 2qb
                     // HUGR
@@ -273,7 +274,7 @@ fn create_commit<'a>(wire: PersistentWire, walker: &Walker<'a>) -> Option<Commit
 
             walker.try_create_commit(
                 PinnedSubgraph::try_from_wires([wire], walker).unwrap(),
-                repl_hugr,
+                RootChecked::try_new(repl_hugr).expect("Root should be DFG."),
                 |node, port| {
                     // map the incoming/outgoing ports of the subgraph to the replacement as
                     // follows: