anchor.diff:              | null -> []
               | x -> [x]
           | None -> []        
  -#endif
   
       /// Use MSBuild to determine the version of the highest installed framework.
       let HighestInstalledNetFrameworkVersionMajorMinor() =
  
positive.code:     /// The list of supported .NET Framework version numbers, using the monikers of the Reference Assemblies folder.
      let SupportedNetFrameworkVersions = set [ Net20; Net30; Net35; Net40; Net45; Net451; (*SL only*) "v5.0" ]
      
  #if __IGNORE_CROSS_PLATFORM_COMPILER
      // Mono doesn't have GetPathToDotNetFramework. In this case we simply don't search this extra directory.
      // When the x-plat compiler is run on Mono this is ok since implementation assembly folder is the same as the target framework folder.
      // When the x-plat compiler is run on Windows/.NET this will curently cause slightly divergent behaviour.
      let GetPathToDotNetFrameworkImlpementationAssemblies _v = []
  #else
      /// Get the path to the .NET Framework implementation assemblies by using ToolLocationHelper.GetPathToDotNetFramework.
      /// This is only used to specify the "last resort" path for assembly resolution.
      let GetPathToDotNetFrameworkImlpementationAssemblies(v) =
  
negative.code:             | null -> []
              | x -> [x]
          | _ -> []
  
  
      let GetPathToDotNetFrameworkReferenceAssembliesFor40Plus(version) = 
          // starting with .Net 4.0, the runtime dirs (WindowsFramework) are never used by MSBuild RAR
  