Fix mypy errors (quantum_info)

[Randl]

Summary

Following discussion, I'm splitting #8187 by module.

Details and comments

There are 8 errors left:

qiskit/quantum_info/synthesis/two_qubit_decompose.py:580: error: Missing positional arguments "num_qubits", "params" in call to "Gate"  [call-arg]
qiskit/quantum_info/synthesis/two_qubit_decompose.py:580: error: Argument 1 to "Gate" has incompatible type "float"; expected "str"  [arg-type]
qiskit/quantum_info/synthesis/two_qubit_decompose.py:583: error: Missing positional arguments "num_qubits", "params" in call to "Gate"  [call-arg]
qiskit/quantum_info/synthesis/two_qubit_decompose.py:583: error: Argument 1 to "Gate" has incompatible type "float"; expected "str"  [arg-type]
qiskit/quantum_info/synthesis/two_qubit_decompose.py:590: error: Missing positional arguments "num_qubits", "params" in call to "Gate"  [call-arg]
qiskit/quantum_info/synthesis/two_qubit_decompose.py:590: error: Argument 1 to "Gate" has incompatible type "float"; expected "str"  [arg-type]
qiskit/quantum_info/synthesis/two_qubit_decompose.py:665: error: Missing positional arguments "num_qubits", "params" in call to "Gate"  [call-arg]
qiskit/quantum_info/synthesis/two_qubit_decompose.py:665: error: Argument 1 to "Gate" has incompatible type "float"; expected "str"  [arg-type]

All are related to the fact that gates, even though inheriting from Gate have different constructor signature. Not sure what the proper fix is.
The ignores are related to python/mypy#1362

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[kevinsung]

The ignores are related to python/mypy#1362

That issue is closed. Do you still get an error if you run with the latest version of mypy?

[coveralls]

Pull Request Test Coverage Report for Build 4117876587

• 5 of 5 (100.0%) changed or added relevant lines in 2 files are covered.
• 5 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.002%) to 85.277%

---

Files with Coverage Reduction	New Missed Lines	%
qiskit/transpiler/passes/synthesis/unitary_synthesis.py	2	93.97%
qiskit/pulse/library/waveform.py	3	91.67%

Totals
Change from base Build 4114140947:	-0.002%
Covered Lines:	67251
Relevant Lines:	78862

---

💛 - Coveralls

[Randl]

The code related to this issue is removed anyway. I've rebased on current master and updated correspondingly

[kevinsung]

Thanks! Are there any more mypy issues in this module? If so, could you report the output?

[Randl]

There are a few left:

out.txt:qiskit/quantum_info/synthesis/two_qubit_decompose.py:585: error: Missing positional arguments "num_qubits", "params" in call to "Gate"  [call-arg]
out.txt:qiskit/quantum_info/synthesis/two_qubit_decompose.py:588: error: Missing positional arguments "num_qubits", "params" in call to "Gate"  [call-arg]
out.txt:qiskit/quantum_info/synthesis/two_qubit_decompose.py:595: error: Missing positional arguments "num_qubits", "params" in call to "Gate"  [call-arg]
out.txt:qiskit/quantum_info/synthesis/two_qubit_decompose.py:670: error: Missing positional arguments "num_qubits", "params" in call to "Gate"  [call-arg]
out.txt:qiskit/quantum_info/synthesis/two_qubit_decompose.py:670: error: Argument 1 to "Gate" has incompatible type "float"; expected "str"  [arg-type]
out.txt:qiskit/quantum_info/synthesis/xx_decompose/decomposer.py:99: error: Item "QuantumCircuit" of "Union[List[Any], QuantumCircuit]" has no attribute "__iter__" (not iterable)  [union-attr]

All except one are since Gate overloads have different constructor parameters. The last one I'm unsure about.

[kevinsung]

The last one seems like it's related to one of your changes, right? Could you please post the mypy outputs both before and after the changes you made?

[Randl]

Ok, this is a consequence of the fact that QuantumCircuit implements getitem but not iter: python/mypy#9737

Not sure what is the appropriate fix? Maybe just adding iter function

[kevinsung]

Shouldn't it be CircuitInstruction instead of QuantumCircuit?

[Randl]

I don't think so. This docstring mentions "circuit"
https://github.com/Qiskit/qiskit-terra/blob/089017cda48fadb7b4d8e7f11a9c5d5074ec5751/qiskit/quantum_info/synthesis/xx_decompose/decomposer.py#L66-L68
and tests use "circuit"
https://github.com/Qiskit/qiskit-terra/blob/089017cda48fadb7b4d8e7f11a9c5d5074ec5751/test/python/quantum_info/xx_decompose/test_decomposer.py#L82-L97
maybe the code should accept both tho.

[kevinsung]

Looking at the code, it seems that

next(iter(self.embodiments.items()), ([], []))

should be a QuantumCircuit. But then embodiment_circuit is actually obtained by indexing into this object:

next(iter(self.embodiments.items()), ([], []))[1]

[Randl]

self.embodiments is a dictionary, so self.embodiments.items() contains tuples, and thus indexing will return the second element of first tuple, i.e., circuit

[kevinsung]

Ah, ok. It seems this line can be significantly simplified by calling self.embodiments.values() instead of items. You can go ahead and make that change if you like, but it's not necessary.

[kevinsung]

Thanks! If you decide to update your other mypy PRs, please include the mypy output both before and after your changes. That would make the review easier.

[Randl]

@kevinsung Thanks! I've added the mypy output after changes, but keeping PRs up-to-date is a bit annoying, so I'm waiting for some of the maintainers to engage on specific PR before updating it. Feel free to ping me if you want me to update some specific ones.