refactor: Remove clone in ExtensionSet::union (#859)

src/builder/dataflow.rs

@@ -55,7 +55,7 @@ impl<T: AsMut<Hugr> + AsRef<Hugr>> DFGBuilder<T> {
             parent,
             NodeType::new(
                 output,
-                input_extensions.map(|inp| inp.union(&signature.extension_reqs)),
+                input_extensions.map(|inp| inp.union(signature.extension_reqs)),
             ),
         )?;
 
@@ -430,7 +430,7 @@ pub(crate) mod test {
         let xb: ExtensionId = "B".try_into().unwrap();
         let xc: ExtensionId = "C".try_into().unwrap();
         let ab_extensions = ExtensionSet::from_iter([xa.clone(), xb.clone()]);
-        let abc_extensions = ab_extensions.clone().union(&xc.clone().into());
+        let abc_extensions = ab_extensions.clone().union(xc.clone().into());
 
         let parent_sig =
             FunctionType::new(type_row![BIT], type_row![BIT]).with_extension_delta(abc_extensions);

src/extension.rs

@@ -455,8 +455,8 @@ impl ExtensionSet {
     }
 
     /// Returns the union of two extension sets.
-    pub fn union(mut self, other: &Self) -> Self {
-        self.0.extend(other.0.iter().cloned());
+    pub fn union(mut self, other: Self) -> Self {
+        self.0.extend(other.0);
         self
     }
 

src/extension/infer.rs

@@ -512,7 +512,7 @@ impl UnificationContext {
                 // to a set which already contained it.
                 Constraint::Plus(r, other_meta) => {
                     if let Some(rs) = self.get_solution(other_meta) {
-                        let rrs = rs.clone().union(r);
+                        let rrs = rs.clone().union(r.clone());
                         match self.get_solution(&meta) {
                             // Let's check that this is right?
                             Some(rs) => {
@@ -725,7 +725,7 @@ impl UnificationContext {
                 .iter()
                 .flat_map(|m| self.get_constraints(m).unwrap())
                 .filter_map(|c| match c {
-                    Constraint::Plus(_, other_m) => solutions.get(&self.resolve(*other_m)),
+                    Constraint::Plus(_, other_m) => solutions.get(&self.resolve(*other_m)).cloned(),
                     Constraint::Equal(_) => None,
                 })
                 .fold(ExtensionSet::new(), ExtensionSet::union);

src/extension/infer/test.rs

@@ -255,7 +255,7 @@ fn dangling_src() -> Result<(), Box<dyn Error>> {
     assert_eq!(hugr.get_nodetype(src.node()).io_extensions().unwrap().1, rs);
     assert_eq!(
         hugr.get_nodetype(mult.node()).io_extensions().unwrap(),
-        (&rs.clone(), rs)
+        (rs.clone(), rs)
     );
     Ok(())
 }
@@ -366,11 +366,11 @@ fn test_conditional_inference() -> Result<(), Box<dyn Error>> {
     for node in [case0_node, case1_node, conditional_node] {
         assert_eq!(
             hugr.get_nodetype(node).io_extensions().unwrap().0,
-            &ExtensionSet::new()
+            ExtensionSet::new()
         );
         assert_eq!(
             hugr.get_nodetype(node).io_extensions().unwrap().0,
-            &ExtensionSet::new()
+            ExtensionSet::new()
         );
     }
     Ok(())
@@ -724,7 +724,10 @@ fn make_looping_cfg(
     bb1_ext: ExtensionSet,
     bb2_ext: ExtensionSet,
 ) -> Result<Hugr, Box<dyn Error>> {
-    let hugr_delta = entry_ext.clone().union(&bb1_ext).union(&bb2_ext);
+    let hugr_delta = entry_ext
+        .clone()
+        .union(bb1_ext.clone())
+        .union(bb2_ext.clone());
 
     let mut hugr = Hugr::new(NodeType::new_open(ops::CFG {
         signature: FunctionType::new(type_row![NAT], type_row![NAT])

src/extension/validate.rs

@@ -31,7 +31,7 @@ impl ExtensionValidator {
                 .map(|s| s.extension_reqs)
                 .unwrap_or_default();
 
-            let outgoing_sol = extension_reqs.union(&incoming_sol);
+            let outgoing_sol = extension_reqs.union(incoming_sol.clone());
 
             extensions.insert((node, Direction::Incoming), incoming_sol);
             extensions.insert((node, Direction::Outgoing), outgoing_sol);

src/hugr.rs

@@ -126,10 +126,10 @@ impl NodeType {
     ///
     /// `None`` if the [Self::input_extensions] is `None`.
     /// Otherwise, will return Some, with the output extensions computed from the node's delta
-    pub fn io_extensions(&self) -> Option<(&ExtensionSet, ExtensionSet)> {
+    pub fn io_extensions(&self) -> Option<(ExtensionSet, ExtensionSet)> {
         self.input_extensions
-            .as_ref()
-            .map(|e| (e, self.op.extension_delta().union(e)))
+            .clone()
+            .map(|e| (e.clone(), self.op.extension_delta().union(e)))
     }
 
     /// Gets the underlying [OpType] i.e. without any [input_extensions]

src/hugr/rewrite/outline_cfg.rs

@@ -72,7 +72,7 @@ impl OutlineCfg {
                     }
                 }
             }
-            extension_delta = extension_delta.union(&o.signature().extension_reqs);
+            extension_delta = extension_delta.union(o.signature().extension_reqs);
             let external_succs = h.output_neighbours(n).filter(|s| !self.blocks.contains(s));
             match external_succs.at_most_one() {
                 Ok(None) => (), // No external successors

src/std_extensions/collections.rs

@@ -91,7 +91,7 @@ impl CustomConst for ListValue {
 
     fn extension_reqs(&self) -> ExtensionSet {
         ExtensionSet::union_over(self.0.iter().map(Value::extension_reqs))
-            .union(&(EXTENSION_NAME.into()))
+            .union(EXTENSION_NAME.into())
     }
 }
 

src/types/signature.rs

@@ -25,7 +25,7 @@ pub struct FunctionType {
 impl FunctionType {
     /// Builder method, add extension_reqs to an FunctionType
     pub fn with_extension_delta(mut self, rs: impl Into<ExtensionSet>) -> Self {
-        self.extension_reqs = self.extension_reqs.union(&rs.into());
+        self.extension_reqs = self.extension_reqs.union(rs.into());
         self
     }