Clang support for __is_assignable intrinsic
MSVC now supports the __is_assignable type trait intrinsic,
to enable easier and more efficient implementation of the
Standard Library's is_assignable trait.
As of Visual Studio 2015 Update 3, the VC Standard Library
implementation uses the new intrinsic unconditionally.
The implementation is pretty straightforward due to the previously
existing is_nothrow_assignable and is_trivially_assignable.
We handle __is_assignable via the same code as the other two except
that we skip the extra checks for nothrow or triviality.
Patch by Dave Bartolomeo!
Differential Revision: http://reviews.llvm.org/D20492
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@270458
91177308-0d34-0410-b5e6-
96231b3b80d8