fix: Make dummy decl names unique

guppy/hugr/hugr.py

@@ -632,10 +632,16 @@ def remove_dummy_nodes(self) -> "Hugr":
         """Replaces dummy ops with external function calls."""
         if self.root is None:
             raise ValueError("Dummy node removal requires a module root node")
+        used_names: dict[str, int] = {}
         for n in list(self.nodes()):
             if isinstance(n, VNode) and isinstance(n.op, ops.DummyOp):
                 name = n.op.name
                 fun_ty = FunctionType(list(n.in_port_types), list(n.out_port_types))
+                if name in used_names:
+                    used_names[name] += 1
+                    name = f"{name}${used_names[name]}"
+                else:
+                    used_names[name] = 0
                 decl = self.add_declare(fun_ty, self.root, name)
                 n.op = ops.Call()
                 self.add_edge(decl.out_port(0), n.add_in_port(fun_ty))

tests/hugr/test_dummy_nodes.py

@@ -0,0 +1,41 @@
+import pytest
+
+from guppy.error import UndefinedPort, InternalGuppyError
+from guppy.guppy_types import FunctionType
+from guppy.hugr import ops
+from guppy.hugr.hugr import Hugr
+from guppy.prelude.builtin import BoolType, IntType
+
+
+def test_single_dummy():
+    g = Hugr()
+    defn = g.add_def(FunctionType([IntType()], [IntType()]), g.root, "test")
+    dfg = g.add_dfg(defn)
+    inp = g.add_input([IntType()], dfg).out_port(0)
+    dummy = g.add_node(
+        ops.DummyOp(name="dummy"), inputs=[inp], output_types=[IntType()], parent=dfg
+    )
+    g.add_output([dummy.out_port(0)], parent=dfg)
+
+    g.remove_dummy_nodes()
+    [decl] = [n for n in g.nodes() if isinstance(n.op, ops.FuncDecl)]
+    assert decl.op.name == "dummy"
+
+
+def test_unique_names():
+    g = Hugr()
+    defn = g.add_def(FunctionType([IntType()], [IntType(), BoolType]), g.root, "test")
+    dfg = g.add_dfg(defn)
+    inp = g.add_input([IntType()], dfg).out_port(0)
+    dummy1 = g.add_node(
+        ops.DummyOp(name="dummy"), inputs=[inp], output_types=[IntType()], parent=dfg
+    )
+    dummy2 = g.add_node(
+        ops.DummyOp(name="dummy"), inputs=[inp], output_types=[BoolType()], parent=dfg
+    )
+    g.add_output([dummy1.out_port(0), dummy2.out_port(0)], parent=dfg)
+
+    g.remove_dummy_nodes()
+    [decl1, decl2] = [n for n in g.nodes() if isinstance(n.op, ops.FuncDecl)]
+    assert {decl1.op.name, decl2.op.name} == {"dummy", "dummy$1"}
+