CircuitOptimizer throws assertion failure on CZs following CNOTs

[ausbin]

The following test QCOR program:

__qpu__ void cz(qreg q) {
    CNOT(q[0], q[1]);
    CZ(q[0], q[1]);
    Measure(q[0]);
    Measure(q[1]);
}

int main() {
    set_shots(1024);
    set_verbose(true);

    auto q = qalloc(2);
    cz(q);
    q.print();
}

will throw the following error when running ./cz after compiling with -opt 1 passed to qcor:

cz: /home/austin/Documents/school/gatech/grad/xacc/xacc/quantum/plugins/optimizers/simple/CircuitOptimizer.cpp:681: bool xacc::quantum::CircuitOptimizer::tryRotationMergingUsingPhasePolynomials(std::shared_ptr<xacc::CompositeInstruction>&): Assertion `instruction->name() == "CNOT"' failed.
Aborted (core dumped)

I believe this is thrown by this line of CircuitOptimizer:

xacc/quantum/plugins/optimizers/simple/CircuitOptimizer.cpp

Line 681 in 4b894ba

assert(instruction->name() == "CNOT");

. I tried to take a look at it and fix it, but I honestly do not quite understand how that part of the code works