title: How to use internal Roslyn classes?
body: <p>What is correct way for using Roslyn API in analizers? 
  Let say I need to fetch info from context.Symbol and it is a field.
  So it is obvious I can cast it to IFieldSymbol but I need to check initializer text. How I can get properties of underlying SourceFieldSymbol? It is Internal!</p>
  
  <p>Reflection ? ;))))</p>