Epic: Default Interface Implementation

[marek-safar]

C#/.NET needs default interface method (dim) support. A lack of default interface is our major API binding problems in Java and iOS (swift/objc).

C#8 release should include default interface methods

C# Feature specification

IL specification draft

CoreCLR is tracking their support at https://github.com/dotnet/coreclr/projects/6

Milestone I

• Port coreclr dim tests to Mono
• Improve runtime support for dim to pass all tests Improve runtime support for dim to pass all tests #6968
• Bundle custom version of csc with dim support Bundle custom version of csc with dim support #7284

Milestone II

• Update dim runtime tests and add support for reflection and reflection.emit Update default interfaces support #11267
• Run Roslyn dim tests as part of acceptance tests
• Switch to official build of Roslyn with dim support