std::move is redundant when it is used to return a local object from a function (eg return std::move(local)): indeed, returning a local object from a function implicitly moves it. Moreover using std::move this way
See https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rf-return-move-local
However, in order to avoid -Wreturn-std-move as well, a Base object is move-constructed
from Derived when required.
