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

Subject: [boost] "is-assignable" compile error using Boost 1.68 / LLVM-Clang / Windows
From: Adam Hartshorne (adam.hartshorne_at_[hidden])
Date: 2018-09-19 18:57:50

I receive the following build error when switching to LLVM toolset in
VS2017 to build code using Boost 1.68. The code builds fine with MSVC
compiler.

1>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'?
1>C:\boost_1_68_0\boost/type_traits/intrinsics.hpp(233): note: expanded
from macro 'BOOST_HAS_TRIVIAL_MOVE_ASSIGN'