-> is an undocumented synonym for => ?

[jbclements]

This program signals an error that doesn't make sense to me, but I think it might be because -> is secretly a synonym for =>:

#lang racket

(require nanopass/base)

(define-language R2a
  (Type (ty)
        (Void)
        (-> ty (ty* ...))
        ))

Specifically, this produces the error:

define-language: found mutually recursive nonterminals in: Type

which doesn't really make any sense to me, but I get the same error if I replace the -> with a =>, and suggests to me that this is interpreting the production as one using a prettifier.