Re: [boost] [optional] Regression in develop

Andrzej Krzemienski wrote:

2017-10-30 13:02 GMT+01:00 Peter Dimov via Boost :

...

That is, the issue only occurs when (a) the compiler is gcc >= 4.9, clang, Sun, (b) the compiler has intrinsic support for __has_trivial_constructor, (c) instantiating the type's default constructor is a hard error.

Is the above a conjunction of (a) and (b) and (c)?

It is.

This sounds like the trait works fine and it is just implementations of `std::pair` that are not SFINAE friendly.

In principle the issue should not be pair-specific and should affect all kinds of user classes, but in practice I've trouble reproducing it with anything else besides std::pair. No idea yet what specifically in std::pair causes it.