Improve error message (#595)

Author: cqc-alec

docs/changelog.md

@@ -4,6 +4,10 @@
 
 # Changelog
 
+## Unreleased
+
+- Update pytket-qir minimum version requirement to 0.24.1.
+
 ## 0.48.0 (May 2025)
 
 - Update pytket minimum version requirement to 2.4.1.

pytket/extensions/quantinuum/backends/quantinuum.py

@@ -74,6 +74,7 @@
 )
 from pytket.qasm import circuit_to_qasm_str
 from pytket.qir import QIRFormat, QIRProfile, pytket_to_qir
+from pytket.qir.conversion.api import ClassicalRegisterWidthError
 from pytket.unit_id import _TEMP_BIT_NAME
 from pytket.utils import prepare_circuit
 from pytket.utils.outcomearray import OutcomeArray
@@ -1220,18 +1221,20 @@ def process_circuits(  # noqa: PLR0912, PLR0915
                         profile = QIRProfile.PYTKET
                     else:
                         profile = QIRProfile.ADAPTIVE
-
-                    quantinuum_circ = b64encode(
-                        cast(
-                            "bytes",
-                            pytket_to_qir(
-                                c0,
-                                "circuit generated by pytket-qir",
-                                QIRFormat.BINARY,
-                                profile=profile,
-                            ),
+                    try:
+                        qir = pytket_to_qir(
+                            c0,
+                            "circuit generated by pytket-qir",
+                            QIRFormat.BINARY,
+                            profile=profile,
                         )
-                    ).decode("utf-8")
+                    except ClassicalRegisterWidthError as e:
+                        raise ValueError(
+                            "Unable to convert pytket circuit to QIR as "
+                            f"it contains a classical register of width {e.width}: "
+                            f"maximum allowed width is {e.max_width}."
+                        ) from None
+                    quantinuum_circ = b64encode(cast("bytes", qir)).decode("utf-8")
 
                     for name, count in Counter(
                         bit.reg_name for bit in c0.bits if not _is_scratch(bit)

setup.py

@@ -46,7 +46,7 @@
     include_package_data=True,
     install_requires=[
         "pytket >= 2.4.1",
-        "pytket-qir >= 0.23.0",
+        "pytket-qir >= 0.24.1",
         "requests >= 2.32.2",
         "types-requests",
         "websockets >= 13.1",