fix(phirgen): don't rely on args when qubits carries correct info (…

…#155)

pytket/phir/phirgen.py

@@ -187,7 +187,7 @@ def convert_gate(op: tk.Op, cmd: tk.Command) -> JsonDict | None:
             qop = {
                 "qop": gate,
                 "returns": [arg_to_bit(cmd.bits[0])],
-                "args": [arg_to_bit(cmd.args[0])],
+                "args": [arg_to_bit(cmd.qubits[0])],
             }
         case ("CX"
             | "CY"

tests/test_phirgen.py

@@ -174,3 +174,17 @@ def test_reordering_classical_conditional() -> None:
         "condition": {"args": [["ctrl", 0], 1], "cop": "=="},
         "true_branch": [{"angles": None, "args": [["q", 0]], "qop": "X"}],
     }
+
+
+def test_conditional_measure() -> None:
+    """From https://github.com/CQCL/pytket-phir/issues/154 ."""
+    c = Circuit(2, 2)
+    c.H(0).H(1)
+    c.Measure(0, 0)
+    c.Measure(1, 1, condition_bits=[0], condition_value=1)
+    phir = json.loads(pytket_to_phir(c))
+    assert phir["ops"][-1] == {
+        "block": "if",
+        "condition": {"cop": "==", "args": [["c", 0], 1]},
+        "true_branch": [{"qop": "Measure", "returns": [["c", 1]], "args": [["q", 1]]}],
+    }