Sure, the desugaring is special treatment, compiler "magic" that is not available at all to other libraries that might like to similarly hook into the map synta

Sure, the desugaring is special treatment, compiler "magic" that is not available at all to other libraries that might like to similarly hook into the map syntax. I was just trying to explain how this does not have to conflict with the claim that the map implementation (the runtime library functions that are called by the desugared version) is plain, regular Go. You could rewrite the map implementation, you just would not get the nice syntax. Compared to Java, it's somewhere in the middle between the regular, entirely "un-magic" implementation of maps and the deeply built in nature of the array primitive, which is not only special at compile time (like Go maps) but also at runtime.