report arity errors in terms of the public API

[bennn]

Fix for #99

Now this program:

#lang racket

(require rackunit)
(check-exn (lambda () 'hi))

Errors with:

check-exn: arity mismatch;
 the expected number of arguments does not match the given number
  given: 1
  arguments...:
   #<procedure:...rackunit/foo.rkt:4:11>
  context...:
   "/..../rackunit/foo.rkt": [running body]
   for-loop
   run-module-instance!125
   perform-require!78

---

This still needs a regression test. (EDIT: added a test)

But also, I'm not happy adding an extra lambda to get the keyword arguments. Suggestions welcome.

[AlexKnauth]

Does this fix #103 as well?

[AlexKnauth]

Would it make sense to flip these two lambdas, making it more like:

  (λ (#:location [location (list 'unknown #f #f #f #f)]
      #:expression [expression 'unknown])
    (procedure-rename
      (λ (formal ... [message #f])
        ..stuff..)
      'pub))

?

It would simplify the id case of the name macro below.

[bennn]

I don't see how that would be simpler by itself. Wouldn't we just go from this:

((apply check-impl args) #:loc .... #:expr ....)

to this:

(apply (check-impl #:loc .... #:expr ....) args)

... maybe its best to remove #:location and #:expression and have define-check expand to code that updates current-check-info manually

[AlexKnauth]

I mean the id case could be simplified from this:

          #'(λ args
               ((apply check-impl args)
                #:location (syntax->location #'loc)
                #:expression 'chk))

To this:

          #'(check-impl
              #:location (syntax->location #'loc)
              #:expression 'chk)

1. (λ args ((apply check-impl args) #:loc .... #:expr ....)) initially.
2. (λ args (apply (check-impl #:loc .... #:expr ....) args)) after flipping the lambdas.
3. (check-impl #:loc .... #:expr ....) after eta-reducing further.

[AlexKnauth]

It also has the benefit of (procedure-arity check-equal?) returning (list 2 3) instead of (arity-at-least 0).

[bennn]

yes this fixes #103

[bennn]

I'm planning to merge this tomorrow night

[AlexKnauth]

To me, this looks good now.

[bennn]

wow, great timing!