private @Nullable ProblemDescriptor getRedundantStringBuilderToStringProblem(final @NotNull PsiMethodCallExpression call) {
      final PsiMethodCallExpression substringCall = PsiTreeUtil.getParentOfType(call, PsiMethodCallExpression.class);
      if (substringCall == null) return null;

      final PsiExpression qualifier = PsiUtil.skipParenthesizedExprDown(substringCall.getMethodExpression().getQualifierExpression());
      if (qualifier != call || !STRING_SUBSTRING.test(substringCall)) return null;

      return getProblem(call, "inspection.redundant.string.call.message");
    }
private @Nullable ProblemDescriptor getRedundantStringBuilderToStringProblem(final @NotNull PsiMethodCallExpression call)