[Default interfaces] Interfaces implemented by arrays

[MichalStrehovsky]

The way default interface methods got implemented in CoreCLR likely means we can't add default interface methods to any of the generic interfaces implemented by arrays.

[MichalStrehovsky]

This is rather difficult to test. CoreLib is not roundtrippable through ILDASM/ILASM (error : Invalid Get method of property 'FirstChar') so I can't really add a new default interface method to, say, ICollection<T>, and test it.

We should have a look at this when we pick up a version of Roslyn that supports default interface methods.

[mangod9]

Hi @MichalStrehovsky is this still an issue post .net 5? Thx

[MichalStrehovsky]

Yes, but since this only affects interfaces that are 100% under our control, we can fix this if/when this becomes an issue (i.e. the libraries team decides it wants to add new methods to e.g. ICollection<T>).