Another attempt to fix compile warning

[kronbichler]

Second attempt to fix the gcc-10 warnings introduced by #15917 - it seems a if constexpr (dim == 0) return; does not make the compiler skip the rest, so I revert to the separate code that was present before 73ab8c4.

[kronbichler]

For reference, the warnings are here: https://cdash.dealii.org/viewBuildError.php?type=1&buildid=1810

[bangerth]

Why write it like this, and not just as follows?

Suggested change

	constexpr int dim = 0;
	AssertThrow(dim > 0, ExcNotImplemented());
	AssertThrow(false, ExcNotImplemented());

[kronbichler]

Good idea, I did this (and changed all other places in the file) in a separate commit.

[bangerth]

Would the warning have gone away if you had put the rest into an else branch?

[kronbichler]

I believe it would, but I do not like to increase of the indentation level that change many more lines. I also note that many other places are using the same technique with separate specializations for 0-d, see the changes I push in a moment for your other remark.

[bangerth]

Out of curiosity: Do you dislike the change because you would not have liked to see the code written in that way to begin with, or because you don't like patches that change indentation? I believe that we should write patches that reflect the code we want, instead of so that they change the minimal number of lines. In other words, our code base should reflect our best effort to produce good and readable code, not reflect its history.

[kronbichler]

I prefer if the code does not indent too much irrespective history, which is why I wrote the early return (I know you prefer the if() ... else ... form). Upon your suggestion, I then realized that the code has many of those template specialization, which I didn't want to touch all. Generally, if I'm given the alternative to indent more or to have separate functions, I would often go with separate functions if the code can be logically split like here. I would not be opposed to switch all occurrences in this class to if constexpr (dim > 0) {...}, because here the indentation is not worrisome. That said, I am certainly guilty of using if (...) return; in some of my code because it can lead to simpler control flow or less indentation when there are multiple conditions, but I also see the point in your preference, so I try to use it only in selected cases.

[bangerth]

I think that's a case of personal preference, and I'll leave it at your discretion :-)

[tamiko]

@bangerth @kronbichler I will check into what gcc-10.4.1 is doing tomorrow. I have a suspicion that the only fix to this warning will be upgrading the compiler to 10.5.0.