Environment

• Qiskit Terra version: 1.0.0.dev0+ac7aca3
• Python version: 3.11
• Operating system: Linux

What is happening?

Trying to convert a circuit with a control flow operation in it to an instruction using qiskit.converters.circuit_to_instruction fails while processing the control flow condition. It is treating it like a c_if legacy style condition even for control flow ops and this causes it to fail with a NotImplementedError because the function is trying to call c_if.

How can we reproduce the issue?

>>> qc = QuantumCircuit(2)
>>> qc.h(0)
<qiskit.circuit.instructionset.InstructionSet object at 0x7f0813ebc280>
>>> qc.cx(0, 1)
<qiskit.circuit.instructionset.InstructionSet object at 0x7f0813ebef80>
>>> qc.measure_all()
>>> with qc.if_test((qc.clbits[0], 0)):
...     qc.x(0)
>>> circuit_to_instruction(qc)

What should happen?

We either should have a descriptive error saying we can't nest control flow operations in an instruction or update the .condition handling in circuit_to_instruction to understand a control flow operation.

Any suggestions?

No response