VS debugger support in the IL interpreter (adding @plnelson)
Manual testing of the VS debugger when using default interfaces
Update our automated debugger tests with at least one successful default interface case and one diamond pattern ambiguous default interface case. The test should cover stepping, func-eval, breakpoint inside the default implementation, and viewing the callstack. We should be able to get someone on @tommcdon's team to help when you are ready.
Looking into the stepping issue I think you were accurate in predicting trouble at that spot. I filed dotnet/coreclr#22059 with my best guess on what in the code needs to be fixed.
Historically teams that build new runtime features own the testing of those features across all the perpendiculars. I think its reasonable for the diagnostics team to assist with adding a new regression test, running it for you in the future + the general consulting/assistance we already did, but not to own this work item all up.