Return void when emitting squin.measure to cirq (#427)

Closes #425

Author: david-pl

src/bloqade/squin/cirq/emit/qubit.py

@@ -49,12 +49,12 @@ def measure_qubit(
     ):
         qbit = frame.get(stmt.qubit)
         frame.circuit.append(cirq.measure(qbit))
-        return ()
+        return (emit.void,)
 
     @impl(qubit.MeasureQubitList)
     def measure_qubit_list(
         self, emit: EmitCirq, frame: EmitCirqFrame, stmt: qubit.MeasureQubitList
     ):
         qbits = frame.get(stmt.qubits)
         frame.circuit.append(cirq.measure(qbits))
-        return ()
+        return (emit.void,)

test/squin/cirq/test_squin_to_cirq.py

@@ -349,4 +349,15 @@ def main():
     assert len(target._cached_circuit_operations) == 2
 
 
-test_return_value()
+def test_return_measurement():
+
+    @squin.kernel
+    def coinflip():
+        qubit = squin.qubit.new(1)[0]
+        squin.gate.h(qubit)
+        return squin.qubit.measure(qubit)
+
+    coinflip.print()
+
+    circuit = squin.cirq.emit_circuit(coinflip, ignore_returns=True)
+    print(circuit)