reflect: StructOf should support embedding types with non-exported methods

[mdempsky]

There's this code in reflect/type.go:

                                    if ift.nameOff(m.name).pkgPath() != "" {
                                            // TODO(sbinet)
                                            panic("reflect: embedded interface with unexported method(s) not implemented")
                                    }

See also #5748.

[rberenguel]

How hard do you reckon this to be @bradfitz @mdempsky ? I'm vaguely familiar with the internals of reflect already (had to do something weird recently and explored it a lot for inspiration), so would love a try if possible to improve my understanding of it.

[ianlancetaylor]

@rberenguel It would be great if you want to work on this, but unfortunately I think it will be pretty hard.

[rberenguel]

Thanks @ianlancetaylor a bad choice then for the first contribution. I'll keep looking!