refactor(Rewrite)!: return impl trait in Rewrite trait (#889)

Get rid of the associated type in Rewrite trait

quantinuum-hugr/src/hugr/rewrite.rs

@@ -18,10 +18,6 @@ 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.
@@ -47,7 +43,7 @@ pub trait Rewrite {
     ///
     /// Two `impl Rewrite`s can be composed if their invalidation sets are
     /// disjoint.
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_>;
+    fn invalidation_set(&self) -> impl Iterator<Item = Node>;
 }
 
 /// Wraps any rewrite into a transaction (i.e. that has no effect upon failure)
@@ -60,9 +56,6 @@ 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> {
@@ -93,7 +86,7 @@ impl<R: Rewrite> Rewrite for Transactional<R> {
     }
 
     #[inline]
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
         self.underlying.invalidation_set()
     }
 }

quantinuum-hugr/src/hugr/rewrite/consts.rs

@@ -29,8 +29,6 @@ impl Rewrite for RemoveLoadConstant {
     // The Const node the LoadConstant was connected to.
     type ApplyResult = Node;
 
-    type InvalidationSet<'a> = iter::Once<Node>;
-
     const UNCHANGED_ON_FAILURE: bool = true;
 
     fn verify(&self, h: &impl HugrView) -> Result<(), Self::Error> {
@@ -64,7 +62,7 @@ impl Rewrite for RemoveLoadConstant {
         Ok(source)
     }
 
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
         iter::once(self.0)
     }
 }
@@ -79,8 +77,6 @@ impl Rewrite for RemoveConst {
     // The parent of the Const node.
     type ApplyResult = Node;
 
-    type InvalidationSet<'a> = iter::Once<Node>;
-
     const UNCHANGED_ON_FAILURE: bool = true;
 
     fn verify(&self, h: &impl HugrView) -> Result<(), Self::Error> {
@@ -108,7 +104,7 @@ impl Rewrite for RemoveConst {
         Ok(parent)
     }
 
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
         iter::once(self.0)
     }
 }

quantinuum-hugr/src/hugr/rewrite/inline_dfg.rs

@@ -25,8 +25,6 @@ impl Rewrite for InlineDFG {
     type ApplyResult = [Node; 3];
     type Error = InlineDFGError;
 
-    type InvalidationSet<'a> = <[Node; 1] as IntoIterator>::IntoIter;
-
     const UNCHANGED_ON_FAILURE: bool = true;
 
     fn verify(&self, h: &impl crate::HugrView) -> Result<(), Self::Error> {
@@ -122,7 +120,7 @@ impl Rewrite for InlineDFG {
         Ok([n, input, output])
     }
 
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
         [self.0.node()].into_iter()
     }
 }

quantinuum-hugr/src/hugr/rewrite/insert_identity.rs

@@ -48,9 +48,6 @@ 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> {
         /*
@@ -90,7 +87,7 @@ impl Rewrite for IdentityInsertion {
     }
 
     #[inline]
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
         iter::once(self.post_node)
     }
 }

quantinuum-hugr/src/hugr/rewrite/outline_cfg.rs

@@ -1,6 +1,5 @@
 //! Rewrite for inserting a CFG-node into the hierarchy containing a subsection of an existing CFG
-use std::collections::{hash_set, HashSet};
-use std::iter;
+use std::collections::HashSet;
 
 use itertools::Itertools;
 use thiserror::Error;
@@ -101,9 +100,6 @@ 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> {
@@ -216,8 +212,7 @@ impl Rewrite for OutlineCfg {
         Ok((new_block, cfg_node))
     }
 
-    #[inline]
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
         self.blocks.iter().copied()
     }
 }

quantinuum-hugr/src/hugr/rewrite/replace.rs

@@ -1,8 +1,6 @@
 //! Implementation of the `Replace` operation.
 
 use std::collections::{HashMap, HashSet, VecDeque};
-use std::iter::Copied;
-use std::slice::Iter;
 
 use itertools::Itertools;
 use thiserror::Error;
@@ -215,10 +213,6 @@ impl Rewrite for Replacement {
 
     type ApplyResult = ();
 
-    type InvalidationSet<'a> = Copied<Iter<'a, Node>>
-    where
-        Self: 'a;
-
     const UNCHANGED_ON_FAILURE: bool = false;
 
     fn verify(&self, h: &impl crate::HugrView) -> Result<(), Self::Error> {
@@ -331,7 +325,7 @@ impl Rewrite for Replacement {
         Ok(())
     }
 
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
         self.removal.iter().copied()
     }
 }

quantinuum-hugr/src/hugr/rewrite/simple_replace.rs

@@ -1,8 +1,6 @@
 //! Implementation of the `SimpleReplace` operation.
 
-use std::collections::{hash_map, HashMap};
-use std::iter::{self, Copied};
-use std::slice;
+use std::collections::HashMap;
 
 use crate::hugr::views::SiblingSubgraph;
 use crate::hugr::{HugrMut, HugrView, NodeMetadataMap, Rewrite};
@@ -55,19 +53,9 @@ impl SimpleReplacement {
     }
 }
 
-type SubgraphNodesIter<'a> = Copied<slice::Iter<'a, Node>>;
-type NuOutNodesIter<'a> = iter::Map<
-    hash_map::Keys<'a, (Node, IncomingPort), IncomingPort>,
-    fn(&'a (Node, IncomingPort)) -> 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;
 
     fn verify(&self, _h: &impl HugrView) -> Result<(), SimpleReplacementError> {
@@ -184,10 +172,9 @@ impl Rewrite for SimpleReplacement {
     }
 
     #[inline]
-    fn invalidation_set(&self) -> Self::InvalidationSet<'_> {
+    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
         let subcirc = self.subgraph.nodes().iter().copied();
-        let get_node: fn(&(Node, IncomingPort)) -> Node = |key| key.0;
-        let out_neighs = self.nu_out.keys().map(get_node);
+        let out_neighs = self.nu_out.keys().map(|key| key.0);
         subcirc.chain(out_neighs)
     }
 }