New Rule Idea: UnsafeAccessorAttribute should not be used on generic methods

[antonioaversa]

Related to C# 12 Zero-overhead member access.

Using UnsafeAccessorAttribute on generic methods results in a System.BadImageFormatException Invalid usage of UnsafeAccessorAttribute.

using System.Runtime.CompilerServices;

[UnsafeAccessor(UnsafeAccessorKind.Constructor)]
extern static UserData<T> CallPrivateConstructor<T>();

_ = CallPrivateConstructor<string>(); // Noncompliant, results in a BadImageFormatException

class UserData<T>
{
    private UserData() { }
    private T Name { get; }
}

Related new rule ideas on C# 12 Zero-overhead member access:

• https://github.com/SonarSource/sonar-dotnet/issues/8154
• https://github.com/SonarSource/sonar-dotnet/issues/8155

[RichardD2]

Annoyingly, the examples in the documentation for .NET 8.0 explicitly show this attribute being used on generic methods, and methods in generic classes.

It's only when you read further down that you see:

Generic parameters are supported since .NET 9.