Refactor: move rewrite inside hugr, Rewrite -> Replace implementing new 'Rewrite' trait

src/hugr.rs

@@ -3,11 +3,13 @@
 mod hugrmut;
 pub mod view;
 
+pub mod replace;
 pub mod serialize;
 pub mod validate;
 
 use derive_more::From;
 pub use hugrmut::HugrMut;
+pub use replace::{Rewrite, RewriteError, RewriteOp};
 pub use validate::ValidationError;
 
 use portgraph::dot::{hier_graph_dot_string_with, DotEdgeStyle};
@@ -16,7 +18,6 @@ use thiserror::Error;
 
 pub use self::view::HugrView;
 use crate::ops::{ModuleOp, OpType};
-use crate::rewrite::{Rewrite, RewriteError};
 use crate::types::EdgeKind;
 
 use html_escape::encode_text_to_string;
@@ -74,29 +75,8 @@ impl Hugr {
     }
 
     /// Applies a rewrite to the graph.
-    pub fn apply_rewrite(mut self, rewrite: Rewrite) -> Result<(), RewriteError> {
-        // Get the open graph for the rewrites, and a HUGR with the additional components.
-        let (rewrite, mut replacement, parents) = rewrite.into_parts();
-
-        // TODO: Use `parents` to update the hierarchy, and keep the internal hierarchy from `replacement`.
-        let _ = parents;
-
-        let node_inserted = |old, new| {
-            std::mem::swap(&mut self.op_types[new], &mut replacement.op_types[old]);
-            // TODO: metadata (Fn parameter ?)
-        };
-        rewrite.apply_with_callbacks(
-            &mut self.graph,
-            |_| {},
-            |_| {},
-            node_inserted,
-            |_, _| {},
-            |_, _| {},
-        )?;
-
-        // TODO: Check types
-
-        Ok(())
+    pub fn apply<E>(&mut self, op: impl RewriteOp<E>) -> Result<(), E> {
+        op.apply(self)
     }
 
     /// Return dot string showing underlying graph and hierarchy side by side.

src/hugr/replace.rs

@@ -0,0 +1,14 @@
+//! Rewrite operations on the HUGR.
+
+#[allow(clippy::module_inception)] // TODO: Rename?
+pub mod rewrite;
+use crate::Hugr;
+pub use rewrite::{OpenHugr, Rewrite, RewriteError};
+
+/// An operation that can be applied to mutate a Hugr
+pub trait RewriteOp<E> {
+    /// Mutate the specified Hugr, or fail with an error.
+    /// Implementations are strongly encouraged not to mutate the Hugr
+    /// if they return an Err.
+    fn apply(self, h: &mut Hugr) -> Result<(), E>;
+}

src/rewrite/rewrite.rs → src/hugr/replace/rewrite.rs

@@ -7,6 +7,7 @@ use portgraph::substitute::OpenGraph;
 use portgraph::{NodeIndex, PortIndex};
 use thiserror::Error;
 
+use super::RewriteOp;
 use crate::Hugr;
 
 /// A subset of the nodes in a graph, and the ports that it is connected to.
@@ -131,6 +132,33 @@ impl Rewrite {
     }
 }
 
+impl RewriteOp<RewriteError> for Rewrite {
+    /// Applies a ReplacementOp to the graph.
+    fn apply(self, h: &mut Hugr) -> Result<(), RewriteError> {
+        // Get the open graph for the rewrites, and a HUGR with the additional components.
+        let (rewrite, mut replacement, parents) = self.into_parts();
+
+        // TODO: Use `parents` to update the hierarchy, and keep the internal hierarchy from `replacement`.
+        let _ = parents;
+
+        let node_inserted = |old, new| {
+            std::mem::swap(&mut h.op_types[new], &mut replacement.op_types[old]);
+            // TODO: metadata (Fn parameter ?)
+        };
+        rewrite.apply_with_callbacks(
+            &mut h.graph,
+            |_| {},
+            |_| {},
+            node_inserted,
+            |_, _| {},
+            |_, _| {},
+        )?;
+
+        // TODO: Check types
+        Ok(())
+    }
+}
+
 /// Error generated when a rewrite fails.
 #[derive(Debug, Clone, Error, PartialEq, Eq)]
 pub enum RewriteError {

src/lib.rs

@@ -16,10 +16,8 @@ pub mod hugr;
 pub mod macros;
 pub mod ops;
 pub mod resource;
-pub mod rewrite;
 pub mod types;
 mod utils;
 
-pub use crate::hugr::{Direction, Hugr, Node, Port, Wire};
+pub use crate::hugr::{Direction, Hugr, Node, Port, Rewrite, RewriteError, Wire};
 pub use crate::resource::Resource;
-pub use crate::rewrite::{Rewrite, RewriteError};