Polymorphism is still a work in progress. You might give the wizards another month before reporting any problems there 
A lot of experimental code to implement arrays is being reimplemented and extended. Follow along in the llvm discourse to know when the switch is flipped to HLFIR.
There’s no need to report the not-yet-implemented messages.
Please report any crashes, bogus messages, or missing checks on GitHub, llvm-project, issues. Tag with flang to get attention.
The main developers advise waiting until the compiler is more complete, but hey, it’s open source so have fun with it!
- Steve