S4039 should not raise for interface default implementations

Rules and Languages
1

Having the following example code:

public interface IBaseInterface
{
    void Method1(string parameter);
}

public interface IDerivedInterface : IBaseInterface
{
    void Method2(int parameter);

    void IBaseInterface.Method1(string parameter) => this.Method2(Convert.ToInt32(parameter, CultureInfo.InvariantCulture)); // S4039
}

As mentioned above, this code raises an issue for rule S4039: “Interface methods should be callable by derived types”.
Why this is raised here? The interface cannot be made sealed, which makes no sense for interfaces.
Is there any alternative to implement such default implementation without triggering the rule?
I think, this is a false-positive.

2

Hi,

I’m sure you’ve told me in other threads, but I have the retention of a tse-tse fly for these things. :sweat_smile: Can you give your context for this? I.e. are you on SonarQube Cloud? SonarQube for IDE (flavor and version)? SonarQube self-managed (flavor and version)?

 
Thx,
Ann

3

Sorry, I omit these information explicitly because I assumed that all current versions have the same problem.
But, ok. Here are the versions I’ve verified this issue:
SonarQube for IDE (Rider extension): 11.15.0.84329
SonarQube Server Developer Edition: v2025.5

1 Like
5

Hi,

You’re in the latest version of SonarQube for IntelliJ/Rider, but you’re connected to a slightly stale version of SonarQube (2026.1 is the current LTA and 2026.2 is the Latest.) However, I don’t see any fixed tickets in Jira for this, so I’m going to flag it for the language devs.

 
Ann