feat: Loosen bound on Patch trait

hugr-core/src/hugr/patch.rs

@@ -13,6 +13,7 @@ pub mod simple_replace;
 
 use crate::HugrView;
 use crate::core::HugrNode;
+use crate::hugr::views::NodesIter;
 use itertools::Itertools;
 pub use port_types::{BoundaryPort, HostPort, ReplacementPort};
 pub use simple_replace::{SimpleReplacement, SimpleReplacementError};
@@ -21,6 +22,8 @@ use super::HugrMut;
 use super::views::ExtractionResult;
 
 /// Verify that a patch application would succeed.
+// TODO: This trait should be parametrised on `H: NodesIter` to match the
+// generality of [`Patch`].
 pub trait PatchVerification {
     /// The type of Error with which this Rewrite may fail
     type Error: std::error::Error;
@@ -66,9 +69,9 @@ pub trait PatchVerification {
 ///
 /// ### When to implement
 ///
-/// For patches that work on any `H: HugrMut`, prefer implementing [`PatchHugrMut`] instead. This
-/// will automatically implement this trait.
-pub trait Patch<H: HugrView>: PatchVerification<Node = H::Node> {
+/// For patches that work on any `H: HugrMut`, prefer implementing
+/// [`PatchHugrMut`] instead. This will automatically implement this trait.
+pub trait Patch<H: NodesIter>: PatchVerification<Node = H::Node> {
     /// The type returned on successful application of the rewrite.
     type Outcome;
 

hugr-core/src/hugr/views.rs

@@ -1,6 +1,7 @@
 //! Read-only access into HUGR graphs and subgraphs.
 
 mod impls;
+mod nodes_iter;
 pub mod petgraph;
 pub mod render;
 mod rerooted;
@@ -16,6 +17,7 @@ use std::collections::HashMap;
 pub use self::petgraph::PetgraphWrapper;
 #[allow(deprecated)]
 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 sibling_subgraph::SiblingSubgraph;

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

@@ -0,0 +1,29 @@
+use crate::{HugrView, core::HugrNode, hugr::views::SiblingSubgraph};
+
+/// A trait for iterating over nodes within a graph view (Hugr, SiblingSubgraph,
+/// etc).
+///
+/// Iterating over nodes within a graph view (Hugr, SiblingSubgraph, etc).
+pub trait NodesIter {
+    /// The type of nodes in the graph.
+    type Node;
+
+    /// Iterate over the nodes in the graph.
+    fn nodes(&self) -> impl Iterator<Item = Self::Node> + '_;
+}
+
+impl<H: HugrView> NodesIter for H {
+    type Node = H::Node;
+
+    fn nodes(&self) -> impl Iterator<Item = Self::Node> + '_ {
+        self.nodes()
+    }
+}
+
+impl<N: HugrNode> NodesIter for SiblingSubgraph<N> {
+    type Node = N;
+
+    fn nodes(&self) -> impl Iterator<Item = Self::Node> + '_ {
+        self.nodes().iter().copied()
+    }
+}