The Boost formal review of Peter Dimov's Variant2 library will take
place April 1 - 10, 2019.
Please consider participating in this review. The success of Boost is
partially a result of the quality review process which is conducted by
the community. You are part of the Boost community. I will be grateful
to receive a review based on whatever level of effort or time you can
Variant2 is a never-valueless C++11/14/17 implementation of std::variant.
From the README:
The class boost::variant2::variant<T...> is an almost conforming
implementation of std::variant with the following differences:
* A converting constructor from, e.g. variant<int, float> to
variant<float, double, int> is provided as an extension;
* The reverse operation, going from variant<float, double, int> to
variant<int, float> is provided as the member function
subset<U...>. (This operation can throw if the current state of the
variant cannot be represented.)
* variant<T...> is not trivial when all contained types are trivial.
To avoid going into a valueless-by-exception state, this
implementation falls back to using double storage unless
* one of the alternatives is the type monostate,
* one of the alternatives has a nonthrowing default constructor, or
* all the contained types are nothrow move constructible.
If the first two bullets don't hold, but the third does, the variant
uses single storage, but emplace constructs a temporary and moves it
into place if the construction of the object can throw. In case this
is undesirable, one can force emplace into always constructing in-
place by adding monostate as one of the alternatives.
Please take an early look at the library and ask questions now. Peter
Dimov is very active on the Cpplang Slack #boost channel; however,
please consider using the Boost Dev or User Mail Lists so that the
entire community might benefit from your conversation.
Note: The repository contains an expected implementation also; however,
that is not being considered in this review.