Add dfg_builder_endo

hugr-core/src/builder/build_traits.rs

@@ -302,6 +302,21 @@ pub trait Dataflow: Container {
         )
     }
 
+    /// Return a builder for a [`crate::ops::DFG`] node, i.e. a nested dataflow subgraph,
+    /// that is endomorphic (the output types are the same as the input types).
+    /// The `inputs` must be an iterable over pairs of the type of the input and
+    /// the corresponding wire.
+    fn dfg_builder_endo(
+        &mut self,
+        inputs: impl IntoIterator<Item = (Type, Wire)>,
+    ) -> Result<DFGBuilder<&mut Hugr>, BuildError> {
+        let (types, input_wires): (Vec<Type>, Vec<Wire>) = inputs.into_iter().unzip();
+        self.dfg_builder_fn(
+            FunctionType::new_endo(types).with_extension_delta(TO_BE_INFERRED),
+            input_wires,
+        )
+    }
+
     /// Return a builder for a [`crate::ops::CFG`] node,
     /// i.e. a nested controlflow subgraph.
     /// The `inputs` must be an iterable over pairs of the type of the input and

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

@@ -195,7 +195,7 @@ mod test {
         }
         let c1 = nonlocal.then(|| make_const(&mut outer));
         let inner = {
-            let mut inner = outer.dfg_builder([(int_ty.clone(), a)], int_ty.clone())?;
+            let mut inner = outer.dfg_builder_endo([(int_ty.clone(), a)])?;
             let [a] = inner.input_wires_arr();
             let c1 = c1.unwrap_or_else(|| make_const(&mut inner))?;
             let a1 = inner.add_dataflow_op(IntOpDef::iadd.with_log_width(6), [a, c1])?;
@@ -344,7 +344,7 @@ mod test {
         let h_a = outer.add_dataflow_op(test_quantum_extension::h_gate(), [a])?;
         let h_b = outer.add_dataflow_op(test_quantum_extension::h_gate(), [b])?;
         let [hb_out] = h_b.outputs_arr();
-        let mut inner = outer.dfg_builder([(QB_T, hb_out)], QB_T)?;
+        let mut inner = outer.dfg_builder_endo([(QB_T, hb_out)])?;
         let [i] = inner.input_wires_arr();
         let f = inner.add_load_value(float_types::ConstF64::new(1.0));
         inner.add_other_wire(inner.input().node(), f.node());