godoc should format interface types more like other types, displaying methods individually

[cpcallen]

In e.g. the documentation for the reflect package, concrete types like Value have their methods listed and documented individually, while interface types like Type do not, but force the reader to grovel through the actual source code of interface to find the methods declared on the type. This is a great inconvenience to the reader, particularly because as a consequence the interface type's methods are not listed in the table of contents.

It seems particularly egregious in cases like reflect.Type where the concrete types that fulfil the interface are all unexported, and the user is unlikely to be creating more. The fact that Type is an interface is of no real interest to the reader, and should not affect the format in which the documentation is presented.

[jimmyfrasche]

duplicate of #5860

[cpcallen]

Drat, didn't see that, despite searching for it. Maybe I was looking only for bugs tagged 'documentation', but I guess it really is a bug against godoc functionality rather than documentation... Sorry!

[ALTree]

Looks like we can close this (we prefer to avoid duplicate issues and this indeed looks like a dup of #5860). Please comment if I'm missing something and this should stay open. Thanks.