For the latest documentation on Visual Studio 2017 RC, see Visual Studio 2017 RC Documentation.

Warning C28226: Annotation cannot also be a PrimOp (in current declaration)

This warning indicates that the named annotation is being declared as a PrimOp, and also was previously declared as a normal annotation. This should not be possible if the standard macros are being used for annotations; this warning is not expected to be seen in normal use.