[eigen] const references (bug 218)

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I have a question/comment on bug 218 (http://eigen.tuxfamily.org/bz/show_bug.cgi?id=218) The bug is closed as wontfix, but I suspect that it might be legitimate, hence my post here.

What happens:
Visual Studio users get the following warning: C4181: qualifier applied to reference type; ignored This happens for example inside MatrixBase<Derived>::cross (OrthoMethods.h, line 46) The offending code is: const typename internal::nested<Derived,2>::type lhs(derived());

Now my question:
Why do we have a const keyword there?
If internal::nested<Derived,2>::type turns out to be a reference type, the const is applied to the reference and not to the referenced type and the warning is legitimate (references are always constant). Also, internal::nested uses ref_selector, and ref_selector<T>::type is already a reference to const T, so no need for an additional const. If internal::nested<Derived,2>::type turns out to be a plain type, the const keyword might help the compiler optimize code, which would however surprise me here. If the const is really helpful, a new member internal::nested::const_type might be more appropriate.


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