Fix parametric global phase in `QuantumCircuit.remove_final_measureme…

…nts`

This was overlooked in the changes of 70901b2; the trick is that
`remove_final_measurements` does fairly deep in-place modifications to
the circuit, despite not logically being an in-place operation, so a lot
of internal data has to be touched and kept in sync.

qiskit/circuit/quantumcircuit.py

@@ -2756,6 +2756,8 @@ def remove_final_measurements(self, inplace: bool = True) -> Optional["QuantumCi
         # Clear instruction info
         circ._data = CircuitData(qubits=circ._data.qubits, reserve=len(circ._data))
         circ._parameter_table.clear()
+        # Repopulate the parameter table with any global-phase entries.
+        circ.global_phase = circ.global_phase
 
         # We must add the clbits first to preserve the original circuit
         # order. This way, add_register never adds clbits and just

test/python/circuit/test_circuit_operations.py

@@ -836,6 +836,24 @@ def test_remove_final_measurements_bit_locations(self):
         self.assertEqual(circuit.find_bit(c0[0]), BitLocations(0, [(c0, 0)]))
         self.assertEqual(circuit.find_bit(c3[0]), BitLocations(1, [(c3, 0)]))
 
+    def test_remove_final_measurements_parametric_global_phase(self):
+        """Test that a parametric global phase is respected in the table afterwards."""
+        a = Parameter("a")
+        qc = QuantumCircuit(2, 2, global_phase=a)
+        qc.h(0)
+        qc.cx(0, 1)
+        qc.measure([0, 1], [0, 1])
+
+        expected = QuantumCircuit(2, global_phase=1)
+        expected.h(0)
+        expected.cx(0, 1)
+
+        self.assertEqual(
+            qc.remove_final_measurements(inplace=False).assign_parameters({a: 1}), expected
+        )
+        qc.remove_final_measurements(inplace=True)
+        self.assertEqual(qc.assign_parameters({a: 1}), expected)
+
     def test_reverse(self):
         """Test reverse method reverses but does not invert."""
         qc = QuantumCircuit(2, 2)