S3906: False positive when using generic type constraint

[antoinebj]

Description

The S3906 rule "Event Handlers should have the correct signature" does not recognize generic types being constrained to EventArgs or to a subclass of it.

Repro steps

1. Create a method or class with a generic type parameter constrained to EventArgs

2. Use the constrained generic type as type parameter for EventHandler<> when declaring an event.

Example:

public class Foo<TEventArgs> where TEventArgs : EventArgs
{
    public event EventHandler<TEventArgs> SomethingHappened; // S3906
}

Expected behavior

No violation of the rule should be detected.

Actual behavior

A violation of the rule is detected.

Known workarounds

Suppressing the message.

Related information

• SonarC# Version 7.14.0.8411
• Visual Studio Version 16.0.3

[andrei-epure-sonarsource]

thanks, @antoinebj for the issue+reproducer. I confirm the behavior in 7.14.