It is grammatically correct, since nouns can be verbed -- chicken can be a noun, verb and even adjective, even though its verb form doesn't have a defined meaning -- it's just meaningless. Think of it like this:

    struct chicken chicken(struct chicken chicken) {
        return chicken.chicken;
    }

This will parse, it just won't compile, since we're missing the definition of struct chicken.

Contrast with "chicken go fly", which is grammatically incorrect, but meaningful.