I came across this while reading bradfitz' camlistore code; I didn't see any extensive documentation or post about that. There is a paragraph in the faq (https

I came across this while reading bradfitz' camlistore code; I didn't see any extensive documentation or post about that. There is a paragraph in the faq (https://golang.org/doc/faq#guarantee_satisfies_interface https://golang.org/doc/faq#guarantee_satisfies_interface) and one in "Effective Go" (https://golang.org/doc/effective_go.html#blank_implements https://golang.org/doc/effective_go.html#blank_implements), but I couldn't find much more than that.