Generic PrimitiveJob and BaseSampler/BaseEstimator

[ikkoham]

Summary

This PR improves type hinting with Generic.
The type of result returned by Primitives.run is made explicit, so it is enabling code completion and improving the user experience.

Details and comments

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[coveralls]

Pull Request Test Coverage Report for Build 4685190880

• 15 of 15 (100.0%) changed or added relevant lines in 7 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.006%) to 85.762%

---

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	2	89.87%

Totals
Change from base Build 4681659057:	0.006%
Covered Lines:	70201
Relevant Lines:	81856

---

💛 - Coveralls

[jakelishman]

It's useful to do this, but I don't think you need to override the derived methods to add the type hints. Deriving a class from Generic means you can define the specialisation during the inheritance, rather than at method resolution. For example, given a file generic.py:

import typing

T = typing.TypeVar("T")

class Base(typing.Generic[T]):
    def f(self) -> T:
        raise NotImplementedError

class Int(Base[int]):
    pass

class Str(Base[str]):
    pass

reveal_type(Base().f())
reveal_type(Int().f())
reveal_type(Str().f())

the result of running mypy on it is:

generic.py:15: note: Revealed type is "<nothing>"
generic.py:16: note: Revealed type is "builtins.int"
generic.py:17: note: Revealed type is "builtins.str"
Success: no issues found in 1 source file

[ikkoham]

@jakelishman Thanks. That's true, but to do so would require making JobV1 (that is return type of BaseEstimator/BaseSampler) Generic. I overrode the method instead of changing JobV1 , although it is a bit hacky.
Can I make JobV1 Generic?

[jakelishman]

Ah sorry, I'd misread the code a bit. Yeah, in the way the primitives typing is currently done, the way you've done things is the best. Making JobV1 generic wouldn't solve the problems here, because BaseEstimator and so on aren't generic, and they define the return value of run to be just Job, which has no methods defined. I think you'd either have to do what you've done and manually override the type hints, or the larger change is to also make BaseEstimator (etc) generic over a TypeVar("JobT", bound=Job) (I think it's covariant in this type too).

[ikkoham]

@jakelishman Thank you for your advice. I updated the code. Is this correct?

[ikkoham]

I believe #9480 will fix the lint error.

[jakelishman]

I can't comment on whether the type bounds you've chosen are precisely what the interface is meant to be (I assume that you're correct), but the implementation of them looks fine to me.

[jakelishman]

I can re-approve once the conflicts are fixed. Looks like it's just super minor stuff.

[ikkoham]

@jakelishman Thank you very much! For the bound, this PR does not should neither strengthen nor weaken the restrictions of the type.