Refactor libmints::IntegralFactory.electric_field() to return ElectricFieldInt

[hmacdope]

Description

Refactor electric_field() to return ElectricFieldInt rather than OneBodyAOInt

Fixes #2793

User API & Changelog headlines

• ElectricFieldInt returned now by IntegralFactory.electric_field()
• Equivalent changes in libmintshelper made to stop immediate static cast

Dev notes & details

• ElectricFieldInt returned now by IntegralFactory.electric_field()
• Equivalent changes in libmintshelper

Checklist

• Tests added for any new features
• All or relevant fraction of full tests run

Status

• Ready for review
• Ready for merge

[maxscheurer]

Isn't the purpose of the integral factory that one does not return the ptr to the specific integral class? Do we want to change the other integral types in the factory, too?

[hmacdope]

Isn't the purpose of the integral factory that one does not return the ptr to the specific integral class? Do we want to change the other integral types in the factory, too?

I was just following a suggestion by @JonathonMisiewicz documented in #2793. Happy to close if required :)

[JonathonMisiewicz]

Isn't the purpose of the integral factory that one does not return the ptr to the specific integral class? Do we want to change the other integral types in the factory, too?

The point of the integral factory is that we don't need to pass the same arguments, over and over. Returning a pointer to the base class rather than the derived class gets us nothing. C++ will cast to the base class when necessary.

While I support changing the other integral types as well, I won't insist on it for this PR.

[hmacdope]

If so shall we push forward for this small change to avoid conflicts with #2775 that would occur if we changed everything to not return base class?

[JonathonMisiewicz]

Fine by me.

[hmacdope]

@JonathonMisiewicz have we had any additional thoughts here? #2775 is probably a blocker

[JonathonMisiewicz]

No. I agree that getting #2775 in first is best.

[JonathonMisiewicz]

After fixing merge conflicts, then per discussion on #2775, there are other methods that need their return types adjusted.