S2583 false positive when using IsNullOrWhitespace after a null check

[pers...@paulhickman.co.uk]

Using SonarAnalyzer.CSharp 7.2.0.5463, the call to string.IsNullOrWhiteSpace below erroneously generates warning S2583 stating the code will not be executed because it always returns false.

void Func(string arg)

{

  if (arg== null)

  {

    throw new ArgumentNullException(nameof(arg));

  }

  if (string.IsNullOrWhiteSpace(arg))

  {

     throw new ArgumentException("is blank", nameof(arg));

  }

}

[valeri....@sonarsource.com]

Hi,

This problem was raised a few days ago in the following comment: https://github.com/SonarSource/sonar-csharp/issues/1347#issuecomment-392527036, you could find explanation why it happens there.

Kind regards,

Valeri