/cc @crawshaw

You can't do it. This is essentially a dup of #16522. Since you can't build a named type with reflect, you can't build a self-referential type.

@ianlancetaylor I don't see how this is essentially a dupe, though it is certainly related (and blocked on) #16522.

With #16522 you could do

s := reflect.StructOf(someFields) //want this to contain n but n doesn't exist yet
n := reflect.NamedOf(s, "S", nil)

but without a mechanism for forward declaration, as mentioned in the OP, how do you add a field to s of type n when the construction of n requires that s was already constructed?

(A related concern came up in #4146 where you would need n to define the signatures of the methods to add to n, but that's easier to handle).

s := reflect.StructOf(someFields) //want this to contain n but n doesn't exist yet
n := reflect.NamedOf(s, "S", nil)

If accepted and implemented, proposal #39528 would solve this