private @Nullable ProblemDescriptor getInternProblem(PsiMethodCallExpression call) {
      return PsiUtil.isConstantExpression(call.getMethodExpression().getQualifierExpression())
             ? getProblem(call, "inspection.redundant.string.intern.on.constant.message")
             : null;
    }
private @Nullable ProblemDescriptor getInternProblem(PsiMethodCallExpression call)