Fix order preservation in align_right

Order was not preserved for non-commutable measurements and controls in the same moment. Reversing the circuit's moments did not reverse the ops within those moments. The subsequent `align_left` could split those ops into separate moments. Then reversing the moments again would have the end result of reversing the order of those operations in the final circuit.

This PR makes sure to reverse the order of ops within the moment prior to the call to `align_left`.

cirq-core/cirq/transformers/align.py

@@ -15,6 +15,7 @@
 """Transformer passes which align operations to the left or right of the circuit."""
 
 import dataclasses
+from locale import currency
 from typing import Optional, TYPE_CHECKING
 from cirq import circuits, ops
 from cirq.transformers import transformer_api
@@ -73,4 +74,11 @@ def align_right(
     """
     if context is not None and context.deep is True:
         context = dataclasses.replace(context, deep=False)
-    return align_left(circuit[::-1], context=context)[::-1]
+    backwards = []
+    for moment in circuit[::-1]:
+        backwards.append(circuits.Moment(reversed(moment.operations)))
+    aligned_backwards = align_left(circuits.Circuit(backwards), context=context)
+    forwards = []
+    for moment in aligned_backwards[::-1]:
+        forwards.append(circuits.Moment(reversed(moment.operations)))
+    return circuits.Circuit(forwards)

cirq-core/cirq/transformers/align_test.py

@@ -208,3 +208,16 @@ def test_classical_control():
     )
     cirq.testing.assert_same_circuits(cirq.align_left(circuit), circuit)
     cirq.testing.assert_same_circuits(cirq.align_right(circuit), circuit)
+
+
+def test_measurement_and_classical_control_same_moment_preserve_order():
+    q0, q1 = cirq.LineQubit.range(2)
+    circuit = cirq.Circuit()
+    op_measure = cirq.measure(q0, key='m')
+    op_controlled = cirq.X(q1).with_classical_controls('m')
+    circuit.append(op_measure)
+    circuit.append(op_controlled, cirq.InsertStrategy.INLINE)
+    circuit = cirq.align_right(circuit)
+    ops_in_order = list(circuit.all_operations())
+    assert ops_in_order[0] == op_measure
+    assert ops_in_order[1] == op_controlled