code: public boolean isApplicable(IMarker marker) {
          ASTVisitor prescanVisitor = getApplicabilityVisitor();
          if (prescanVisitor instanceof ApplicabilityVisitor) {       //this has an implicit null check
              return findApplicability(prescanVisitor, marker);
          }
          return true;
      }
docs: If getApplicabilityVisitor() is overwritten, this checks
  to see if this resolution applies to the code at the given marker.
  
  @param marker
  @return true if this resolution should be visible to the user at the given marker