Hi all,
The racket program below exhibits behavior that I think is a bug. When using
define/contract (and I believe with-contract), contracts seem to get applied to
values later than expected. In particular, in the following example I expect
all uses of the variable “test” to see the wrapper added by the contract.
Instead, applications see the projection but inspecting the value without
invoking it does not.
Thanks,
Scott
#lang racket
(require rackunit)
(module test racket
(provide wrapped? (contract-out (test2 coerce-to-wrapped)) test)
(define-values (prop:wrapped wrapped? prop-wrapped-accessor)
(make-impersonator-property 'wrapped))
(define (wrap value)
(let* ([wrapped (λ () (printf "Unwrapping ~a~n" value) value)])
(impersonate-procedure
wrapped
#f
prop:wrapped
#t)))
(define coerce-to-wrapped
(make-contract #:name "wrap"
#:projection
(λ (blame)
(λ (value)
(wrap value)))))
(define/contract (test)
coerce-to-wrapped
5)
(define (test2)
42))
(require 'test)
(check-true (wrapped? test)) ; Should return true!
(check-true (wrapped? test2)) ; Should return true!
(check-equal? ((test)) 5) ; test is in fact wrapped, must invoke twice to use
the original procedure
(check-true (procedure? (test))) ; result of (test) is the unwrapped procedure
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