https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57248
--- Comment #7 from Daniel Krügler <daniel.kruegler at googlemail dot com> --- (In reply to Paolo Carlini from comment #6) > However, it's true that all the up to > date compilers I have at hand reject it with the same kind of error about > get at: > > return std::get<index(array)>(t1); > > like for my reduced testcase in Comment #5. Ouch, you are right - I overlooked the very important fact that *within* function extract the expression index(array) cannot be a constant expression, because we have an argument value involved! In the context of a constexpr function any argument value itself cannot be a constant expression, because the decision for something being a constant expression is always context-independent. I'm very sorry for having mislead Paolo with my original remark, indeed the original test case is *invalid* because it is based on the assumption that a constexpr function argument itself could be a constant expression.
