Skip check-satisfied in stepper

[shhyou]

If I tested it correctly, the stepper from Racket v7 previously skips check-satisfied and the current bugs in it are unintentional. At some point, the stepper from Racket v8 no longer ignores check-satisfied and begins to step through all the with-handlers internal code or even breaks for non-identifier predicates.

This PR works around #232 and restores the previous behavior for check-satisfied by completely ignoring them. Proper support of check-satisfied is needed in the future.

[mikesperber]

Looks good to me. (Even though I don't rememember changing this particular piece of code.)

[shhyou]

@mikesperber Yes, I think the code is never modified. I suppose these behavior changes are the unintended consequences of a combination of test engine changes and stepper changes elsewhere.

For this test case:

(check-expect 1 (+ 1 1))
(check-satisfied (* 2 2) even?)
(check-expect 3 (+ 1 2))

The stepper ignored (check-satisfied (* 2 2) even?) for Racket v8.2 and below. Starting from Racket v8.3 and above, it first shows (... {(* 2 2)} ...) -> (... {4} ...) and then begins to walk through this.

(let ((with-handlers-predicate1
        exn:fail:contract:arity?)
       (with-handlers-handler2
        (lambda (exn)
          (let ((msg (exn-message exn)))
            (let ((msg1
                   (regexp-match
                    (pregexp
                     "(.*): arity mismatch")
                    msg)))
              (cond
               (msg1
                (let ((raised-name (cadr msg1)))
                  (if (equal?
                       "even?"
                       raised-name)
                    (error-check
                     (lambda (v) #false)
                     "even?"
                     SATISFIED-FMT
                     #true)
                    (raise exn))))))))))
   (let ((bpz
          (continuation-mark-set-first
           #false
           break-enabled-key)))
     (call-handled-body
      bpz
      (lambda (e)
        (select-handler/no-breaks
         e
         bpz
         (list
          (cons
           with-handlers-predicate1
           with-handlers-handler2))))
      (lambda () (even? 4)))))

For the other two cases (e.g. (check-satisfied (+ 2 3) (lambda (n) (even? (sub1 n)))) (check-expect 3 (+ 1 2))), the stepper exhibits different errors:

• Racket v7.9 and below: break-reconstruction: held-exp-list not empty when a double-break occurred
• Racket v8.0 and above: the stepper first shows

  (do-check-satisfied
   (lambda () (+ 2 3))
   {(let ((p? (lambda (n) (even? (sub1 n)))))
     (let ((name (object-name p?)))
       (if (if (procedure? p?)
             (procedure-arity-includes? p? 1)
             #false)
         (void)
         (let ()
           (if name
             (error-check
              (lambda (v) #false)
              name
              SATISFIED-FMT
              #true)
             (error-check
              (lambda (v) #false)
              p?
              SATISFIED-FMT
              #true)))))
     p?)}
   "unknown name"
   (kernel:srcloc '3-unsaved-editor 1 0 1 55))
  ->
  {(define p?_0 (lambda (n) (even? (sub1 n))))}
  (do-check-satisfied
   (lambda () (+ 2 3))
   {(values
    (let ((name (object-name p?_0)))
      (if (if (procedure? p?_0)
            (procedure-arity-includes? p?_0 1)
            #false)
        (void)
        (let ()
          (if name
            (error-check
             (lambda (v) #false)
             name
             SATISFIED-FMT
             #true)
            (error-check
             (lambda (v) #false)
             p?_0
             SATISFIED-FMT
             #true)))))
    p?_0)}
   "unknown name"
   (kernel:srcloc '3-unsaved-editor 1 0 1 55))

  and then raises the error lookup-binding: variable not found in environment: lifter-p?-0.