[boost] [fusion] Compilation errors on Intel compiler (C++14)

Subject: [boost] [fusion] Compilation errors on Intel compiler (C++14)
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2016-12-06 11:46:03

Hi,

I'm seeing compilation errors coming from Boost.Fusion headers on 
Sandia-intel-17.0-c++14:

http://www.boost.org/development/tests/develop/developer/output/Sandia-intel-17-0-c++14-boost-bin-v2-libs-log-test-core-test-intel-linux-debug-threading-multi.html

Notably, the same tests compile fine in C++11 mode on the same compiler, 
which makes me think that is related to C++14 mode specifically. Looking 
at the code, it seems the compiler makes constexpr functions implicitly 
const-qualified even though it shouldn't in C++14 mode, so it's likely a 
compiler bug. Still, is it possible to add a workaround?