Improve error message for invalid measurement in adjoint() region

doc/releases/changelog-dev.md

@@ -20,9 +20,13 @@
 * `from_plxpr` now uses the `qml.capture.PlxprInterpreter` class for reduced code duplication.
   [(#1398)](https://github.com/PennyLaneAI/catalyst/pull/1398)
 
+* Improve the error message for invalid measurement in `adjoin()` or `ctrl()` region.
+  [(#1425)](https://github.com/PennyLaneAI/catalyst/pull/1425)
+
 * Replace `ValueRange` with `ResultRange` and `Value` with `OpResult` to better align with the semantics of `**QubitResult()` functions like `getNonCtrlQubitResults()`. This change ensures clearer intent and usage. Improve the `matchAndRewrite` function by using `replaceAllUsesWith` instead of for loop.
   [(#1426)](https://github.com/PennyLaneAI/catalyst/pull/1426)
 
+
 <h3>Documentation 📝</h3>
 
 <h3>Contributors ✍️</h3>
@@ -31,4 +35,4 @@ This release contains contributions from (in alphabetical order):
 
 Christina Lee
 Mehrdad Malekmohammadi
-Sengthai Heng
+Sengthai Heng

frontend/catalyst/api_extensions/quantum_operators.py

@@ -712,14 +712,14 @@ def ctrl_distribute(
 def _check_no_measurements(tape: QuantumTape) -> None:
     """Check the nested quantum tape for the absense of quantum measurements of any kind"""
 
-    msg = "Quantum measurements are not allowed"
-
     if len(tape.measurements) > 0:
-        raise ValueError(msg)
+        raise ValueError("Quantum measurements are not allowed")
     for op in tape.operations:
         if has_nested_tapes(op):
             for r in [r for r in op.regions if r.quantum_tape is not None]:
                 _check_no_measurements(r.quantum_tape)
         else:
             if isinstance(op, MidCircuitMeasure):
-                raise ValueError(msg)
+                raise ValueError(
+                    "Measurements cannot be used within an adjoint() or ctrl() region."
+                )

frontend/test/pytest/test_quantum_control.py

@@ -290,7 +290,7 @@ def _func1():
             C_ctrl(_func1, control=[1], control_values=[True])()
             return qml.state()
 
-        with pytest.raises(ValueError, match="measurements are not allowed"):
+        with pytest.raises(ValueError, match="Measurements cannot be used"):
             qjit(circuit)(0.1)
 
     def test_qctrl_no_end_circuit_measurements(self, backend):