Deprecating isinstance(qr[0], tuple) #2474 causes major performance regression

[nonhermitian]

Information

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

What is the current behavior?

This has caused major performance regressions as discussed in #2474.

Steps to reproduce the problem

What is the expected behavior?

Suggested solutions

[mtreinish]

I was concerned that #2474 would have a performance impact, guess it really did.

I wonder why we actually need the Bit classes, considering the backwards compat issues they cause is there actually a benefit to having them over just using the tuple like before? I'd rather just revert all of #2414 then revert just the backwards compat fix.

[mtreinish]

I went ahead and pushed up patch to revert those new classes: #2499 we can discuss that approach there.

[ajavadia]

closed by #2511