Merge inherited interface methods according to variance

[alrz]

interface ISomeInterface<in T> {
  void M(T arg);
}

interface IBase : ISomeInterface<object>;

interface IDerived : IBase, ISomeInterface<string> {
   // uncomment to resolve the error
   // void ISomeInterface<string>.M(string obj) => M(obj as object); // calls base
}
class C : IDerived {
  // error: method `M(string)` is not implemented
  public void M(object arg) { }
}

Could the line with explicit implementation gets generated by the compiler? (that is, if the runtime requires it)

[HaloFour]

That feels like something that perhaps the runtime should be doing rather than relying on the compiler to silently emit an explicit implementation bridge method? Contravariant parameter types feel like a real can of worms, though.

[alrz]

That feels like something that perhaps the runtime should be doing

I tried it in sharplap, it seems like it already passes the verification (sharplab.io)

Either way the compiler needs to expose this support by not requiring the missing exact implementations.

[HaloFour]

Interesting, didn't know the runtime did that :D