Re: [boost] [outcome] High level summary of review feedback accepted so far

On 31 May 2017 at 21:34, Niall Douglas via Boost wrote:

On 31/05/2017 17:42, Vicente J. Botet Escriba wrote:

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Le 31/05/2017 à 12:55, Niall Douglas via Boost a écrit :

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I guess, ultimately, the question to be answered here is how much like std::variant<...> should Outcome and/or Expected be? std::variant<...> doesn't implement completely unchecked observers like optional's operator*(), the best you can get is a nulled pointer observer, no silent reinterpret_cast.

When I started the Expected proposal Variant was not yet there. I believe that we could add the following from variant: * visit * index * get_if/value_if * get

Apart from the lack of never empty guarantee (which can be worked around), there appears to be no good reason to not use std::variant to implement std::expected.

Well, apart from poor quality of implementation of std::variant sometimes. For example, libstdc++'s for GCC 7.1 appears to always use type erased memory allocation. Which, frankly, is daft in C++ 14 when you are storing either an int or a std::error_code. I would also assume that std::bad_alloc can be thrown from libstdc++'s std::variant<> :(

Huh? Where do you see this?