qiskit/releasenotes/notes/0.45/qasm2-fix-zero-op-barrier-4...

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fixes:
- |
The OpenQASM 2 parser (:func:`.qasm2.load` and :func:`~.qasm2.loads`) running in ``strict`` mode
will now correctly emit an error if a ``barrier`` statement has no arguments. When running in
the (default) more permissive mode, an argument-less ``barrier`` statement will continue to
cause a barrier on all qubits currently in scope (the qubits a gate definition affects, or all
the qubits defined by a program, if the statement is in a gate body or in the global scope,
respectively).
- |
The OpenQASM 2 exporter (:meth:`.QuantumCircuit.qasm`) will now no longer attempt
to output ``barrier`` statements that act on no qubits. Such a barrier statement has no effect
in Qiskit either, but is invalid OpenQASM 2.