feat: Move SimpleReplace::invalidation_set to the Rewrite trait (#…

…602)

Closes #601

src/hugr/rewrite.rs

@@ -4,7 +4,7 @@ pub mod insert_identity;
 pub mod outline_cfg;
 pub mod simple_replace;
 
-use crate::{Hugr, HugrView};
+use crate::{Hugr, HugrView, Node};
 pub use simple_replace::{SimpleReplacement, SimpleReplacementError};
 
 use super::HugrMut;
@@ -15,6 +15,11 @@ pub trait Rewrite {
     type Error: std::error::Error;
     /// The type returned on successful application of the rewrite.
     type ApplyResult;
+    /// The node iterator returned by [`Rewrite::invalidation_set`]
+    type InvalidationSet<'a>: Iterator<Item = Node> + 'a
+    where
+        Self: 'a;
+
     /// If `true`, [self.apply]'s of this rewrite guarantee that they do not mutate the Hugr when they return an Err.
     /// If `false`, there is no guarantee; the Hugr should be assumed invalid when Err is returned.
     const UNCHANGED_ON_FAILURE: bool;
@@ -33,6 +38,13 @@ pub trait Rewrite {
     /// implementations may begin with `assert!(h.validate())`, with `debug_assert!(h.validate())`
     /// being preferred.
     fn apply(self, h: &mut impl HugrMut) -> Result<Self::ApplyResult, Self::Error>;
+
+    /// Returns a set of nodes referenced by the rewrite. Modifying any of these
+    /// nodes will invalidate it.
+    ///
+    /// Two `impl Rewrite`s can be composed if their invalidation sets are
+    /// disjoint.
+    fn invalidation_set(&self) -> Self::InvalidationSet<'_>;
 }
 
 /// Wraps any rewrite into a transaction (i.e. that has no effect upon failure)
@@ -45,6 +57,9 @@ pub struct Transactional<R> {
 impl<R: Rewrite> Rewrite for Transactional<R> {
     type Error = R::Error;
     type ApplyResult = R::ApplyResult;
+    type InvalidationSet<'a> = R::InvalidationSet<'a>
+        where
+            Self: 'a;
     const UNCHANGED_ON_FAILURE: bool = true;
 
     fn verify(&self, h: &impl HugrView) -> Result<(), Self::Error> {
@@ -72,4 +87,9 @@ impl<R: Rewrite> Rewrite for Transactional<R> {
         }
         r
     }
+
+    #[inline]
+    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+        self.underlying.invalidation_set()
+    }
 }

src/hugr/rewrite/insert_identity.rs

@@ -1,5 +1,7 @@
 //! Implementation of the `InsertIdentity` operation.
 
+use std::iter;
+
 use crate::hugr::{HugrMut, Node};
 use crate::ops::{LeafOp, OpTag, OpTrait};
 use crate::types::EdgeKind;
@@ -51,6 +53,9 @@ impl Rewrite for IdentityInsertion {
     type Error = IdentityInsertionError;
     /// The inserted node.
     type ApplyResult = Node;
+    type InvalidationSet<'a> = iter::Once<Node>
+    where
+        Self: 'a;
     const UNCHANGED_ON_FAILURE: bool = true;
     fn verify(&self, _h: &impl HugrView) -> Result<(), IdentityInsertionError> {
         /*
@@ -98,6 +103,11 @@ impl Rewrite for IdentityInsertion {
             .expect("Should only fail if ports don't exist.");
         Ok(new_node)
     }
+
+    #[inline]
+    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+        iter::once(self.post_node)
+    }
 }
 
 #[cfg(test)]

src/hugr/rewrite/outline_cfg.rs

@@ -1,5 +1,6 @@
 //! Rewrite for inserting a CFG-node into the hierarchy containing a subsection of an existing CFG
-use std::collections::HashSet;
+use std::collections::{hash_set, HashSet};
+use std::iter;
 
 use itertools::Itertools;
 use thiserror::Error;
@@ -97,6 +98,9 @@ impl Rewrite for OutlineCfg {
     ///
     /// [CFG]: OpType::CFG
     type ApplyResult = (Node, Node);
+    type InvalidationSet<'a> = iter::Copied<hash_set::Iter<'a, Node>>
+        where
+            Self: 'a;
 
     const UNCHANGED_ON_FAILURE: bool = true;
     fn verify(&self, h: &impl HugrView) -> Result<(), OutlineCfgError> {
@@ -211,6 +215,11 @@ impl Rewrite for OutlineCfg {
 
         Ok((new_block, cfg_node))
     }
+
+    #[inline]
+    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+        self.blocks.iter().copied()
+    }
 }
 
 /// Errors that can occur in expressing an OutlineCfg rewrite.

src/hugr/rewrite/simple_replace.rs

@@ -1,6 +1,8 @@
 //! Implementation of the `SimpleReplace` operation.
 
-use std::collections::HashMap;
+use std::collections::{hash_map, HashMap};
+use std::iter::{self, Copied};
+use std::slice;
 
 use itertools::Itertools;
 
@@ -56,23 +58,18 @@ impl SimpleReplacement {
     pub fn subgraph(&self) -> &SiblingSubgraph {
         &self.subgraph
     }
-
-    /// Returns a set of nodes referenced by the replacement. Modifying any
-    /// these nodes will invalidate the replacement.
-    ///
-    /// Two `SimpleReplacement`s can be composed if their affected nodes are
-    /// disjoint.
-    #[inline]
-    pub fn invalidation_set(&self) -> impl Iterator<Item = Node> + '_ {
-        let subcirc = self.subgraph.nodes().iter().copied();
-        let out_neighs = self.nu_out.keys().map(|&(n, _)| n);
-        subcirc.chain(out_neighs)
-    }
 }
 
+type SubgraphNodesIter<'a> = Copied<slice::Iter<'a, Node>>;
+type NuOutNodesIter<'a> =
+    iter::Map<hash_map::Keys<'a, (Node, Port), Port>, fn(&'a (Node, Port)) -> Node>;
+
 impl Rewrite for SimpleReplacement {
     type Error = SimpleReplacementError;
     type ApplyResult = ();
+    type InvalidationSet<'a> = iter::Chain<SubgraphNodesIter<'a>, NuOutNodesIter<'a>>
+    where
+        Self: 'a;
 
     const UNCHANGED_ON_FAILURE: bool = true;
 
@@ -197,6 +194,14 @@ impl Rewrite for SimpleReplacement {
         }
         Ok(())
     }
+
+    #[inline]
+    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+        let subcirc = self.subgraph.nodes().iter().copied();
+        let get_node: fn(&(Node, Port)) -> Node = |key: &(Node, Port)| key.0;
+        let out_neighs = self.nu_out.keys().map(get_node);
+        subcirc.chain(out_neighs)
+    }
 }
 
 /// Error from a [`SimpleReplacement`] operation.
@@ -227,7 +232,7 @@ pub(in crate::hugr::rewrite) mod test {
     use crate::extension::prelude::BOOL_T;
     use crate::extension::{EMPTY_REG, PRELUDE_REGISTRY};
     use crate::hugr::views::{HugrView, SiblingSubgraph};
-    use crate::hugr::{Hugr, HugrMut, Node};
+    use crate::hugr::{Hugr, HugrMut, Node, Rewrite};
     use crate::ops::OpTag;
     use crate::ops::{OpTrait, OpType};
     use crate::std_extensions::logic::test::and_op;