Improve traits of Boost.Move

[Antony Polukhin]

Since boost 1.54.0 we have the following traits:

has_trivial_move_assign has_trivial_move_constructor is_nothrow_move_assignable is_nothrow_move_constructible

It means that has_nothrow_move trait in boost/move/traits.cpp can be improved.

[Ion Gaztañaga]

Fixed in revision 85182

[Antony Polukhin]

I'm afraid that the improved trait breaks one of the tests in libs/move/test/move.hpp.

Following assert:

   BOOST_STATIC_ASSERT((boost::has_nothrow_move<copyable>::value == false));

will be failing now. According to C++11 Standard is_nothrow_move_constructible evaluates to true if the following code does not throw:

copyable var(std::move(nonconst_copyable_variable))

Such code does not throw even if the copyable has no move constructor, but has a nothrow copy constructor.

Following solution could be used to fix tests:

   // Attempt to move construct `copyable` type won't throw exceptions in C++03 and C++11 
   BOOST_STATIC_ASSERT((boost::has_nothrow_move<copyable>::value == true));

[Ion Gaztañaga]

I think that would fix the test only for compilers that can deduce it won't throw. I think we should delete that line as we don't know what the compiler will deduce.

[Antony Polukhin]

Replying to igaztanaga:

I think that would fix the test only for compilers that can deduce it won't throw. I think we should delete that line as we don't know what the compiler will deduce.

I agree. is_nothrow_move_assignable and is_nothrow_move_constructible traits are covered by tests in Boost.TypeTraits. Test in Boost.Move mainly duplicates those.