Cannot build a circuit from qasm with an ecr gate

[nonhermitian]

Information

• Qiskit Terra version: latest
• Python version:
• Operating system:

What is the current behavior?

In trying to build a circuit from qasm using an ecr gate:

['OPENQASM 2.0;',
 'include "qelib1.inc";',
 'gate ecr q0, q1 { U(3*pi/2, pi, pi) q0; U(pi/2, pi/2, 3*pi/2) q1; CX q0, q1; }',
 'qreg q[2];',
 'creg meas[2];',
 'h q[0];',
 'ecr q[0],q[1];',
 'barrier q[0],q[1];',
 'measure q[0] -> meas[0];',
 'measure q[1] -> meas[1];',
 '']

QuantumCircuit.from_qasm_str(qasm_str)

I get the following error:

 File "/opt/conda/lib/python3.7/site-packages/qiskit/converters/ast_to_dag.py", line 401, in _gate_rules_to_qiskit_circuit
    op = self._create_op(child_op.name, params=eparams)
AttributeError: 'UniversalUnitary' object has no attribute 'name'

Steps to reproduce the problem

What is the expected behavior?

Suggested solutions

[kdk]

Looks like .name is never set for the built-in Cnot and UniversalUnitary classes (so, this works if U/CX are replaced with u/cx). Any idea why @1ucian0 ?

[francabrera]

in addition to that, should this gate be included in the qelib1.inc https://github.com/Qiskit/qiskit-terra/blob/master/qiskit/qasm/libs/qelib1.inc being a basis gate?

[1ucian0]

I think the problem is about scoping. The following works:

qasm_str = '\n'.join(['OPENQASM 2.0;',
                      'include "qelib1.inc";',
                      'qreg q[2];',
                      'U(3*pi/2, pi, pi) q[0];',
                      'CX q[0], q[1];',
                      ''])

print(QuantumCircuit.from_qasm_str(qasm_str))

[1ucian0]

in addition to that, should this gate be included in the qelib1.inc https://github.com/Qiskit/qiskit-terra/blob/master/qiskit/qasm/libs/qelib1.inc being a basis gate?

We are moving towards leaving qelib1.inc fixed, following the paper definition. See #4312 and #6125