We have Roslyn Analyzers written for VS2013 though its not officially supported by MSFT now. We decided to upgrade those to VS2015. The APIs are drastically different but we managed to do it. The VS2013 analyzer dlls were normal .Net class libraries. But in VS2015, it specifically demands the class libraries to be portable. I don't think VS2015 is portable.
Are there any reasons for enforcing portability for Roslyn analyzer dlls? One reason I could think of is to run the Analyzers all the places .Net program can be compiled. Are there any other reasons?