define-metafunction does not check type signature on LHS

#lang racket
(require redex)

(define-language A (N ::= 0 1 2))

(define-metafunction A
  flip : N -> N
  [(flip 1) ()]
  [(flip ()) 1])

(term (flip 1))
; flip: codomain test failed for (), call was (flip 1) [,bt for context]
(term (flip ()))
; flip: (flip ()) is not in my domain [,bt for context]

Ideally, the clauses in the definition of flip would be rejected because () does not match the grammar N, so they can never be used correctly. Checking #:pre and #:post conditions would also be great, but I'm not sure this is possible. (Also I wouldn't be too surprised if it is possible to write expressions that can't be typechecked at function declaration time, but there are lots of examples like this one where the pattern definitely has empty intersection with the grammar, so an error message seems warranted.)

Start at the define-metafunction entry point and reproduce the example showing clauses whose left-hand patterns do not match N. Determine how declaration-time grammar checks should report the invalid clauses, and verify that valid definitions and the existing runtime errors remain unchanged. The issue also mentions #:pre and #:post checks as a possible follow-up or scope question.