[jaekwon]

The inner structs (of which the outer writer struct is composed) cannot access any of the functionality or fields outside of itself. Each inner struct is completely encapsulated, so you can't override an inner struct method and expect the inner struct's behavior to change.

The accessibility of inner struct methods from the outer struct is a syntactic convenience.

Java: https://gist.github.com/jaekwon/8025b9f3a482b3219a21 Go: https://gist.github.com/jaekwon/0f6e5555ab6a592aa4c8

Once you Go, you never go back. ;)

[pcwalton]

There are also no virtual methods with struct composition. If B embeds A, "upcasting" an instance of B to A will not allow you to call any methods on B.