Re: [boost] "is-assignable" compile error using Boost 1.68 / LLVM-Clang / Windows

Subject: Re: [boost] "is-assignable" compile error using Boost 1.68 / LLVM-Clang / Windows
From: John Maddock (jz.maddock_at_[hidden])
Date: 2018-09-20 07:41:36

On 20/09/2018 06:40, Gavin Lambert via Boost wrote:
> On 20/09/2018 16:47, Adam Hartshorne wrote:
>> Looks like boost::variant is the problem.
>
> No, those are just plain includes.  Nothing to see there.
>
>> 2>C:\boost_1_68_0\boost/type_traits/has_trivial_move_assign.hpp(49): 
>> error
>> : no template named 'is_assignable'; did you mean 'std::is_assignable'?
>> 2>C:\boost_1_68_0\boost/type_traits/intrinsics.hpp(233): note: expanded
>> from macro 'BOOST_HAS_TRIVIAL_MOVE_ASSIGN'
>
> The problem is actually here.
>
> As degski suggests, it's probably a compiler detection quirk where the 
> BOOST_HAS_TRIVIAL_MOVE_ASSIGN macro has been defined because 
> __has_feature exists but <boost/type_traits/is_assignable.hpp> was not 
> included because __clang doesn't exist.  Or something like that.

Just to be clear, it's a flat out bug in type_traits and has been fixed 
for the next release (which doesn't help the OP), a workaround would be 
to add:

#include <boost/type_traits/is_assignable.hpp>

before any other boost includes in your program.

Best, John.

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