Andrzej Krzemienski wrote:
Specification of function `emplace<I>()`: It says:
On exception: If the list of alternatives contains monostate, the contained value is either unchanged, or monostate{};
In what situation on exception is the contained value left unchanged? This question applies to the next bullet as well.
I prefer to leave this unspecified.
swap(): What does it throw and when? Other functions specify it but this one does not.
swap() is defined as equivalent to code sequences (depending on whether the indices match), so the effects, including exceptions thrown, are the effects of those code sequences.
get<I>(): Specification says,
If v.index() is I, returns a reference to the object stored in the variant. Otherwise, throws bad_variant_access.
This means that if I provide an index that is far greater than `sizeof...(T)`, the program should compile fine and throw an exception at run-time.
Not quite, because get<> returns variant_alternative_t
According to the specs, the following should work:
``` void f() {} variant2::visit(f); ``` which is not incorrect, but strange.
This is also the case with std::variant if I'm not mistaken? The purpose is probably to support variant<> parameter packs in a consistent way, even when the pack is empty.