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document/test optional argument of impersonator propertry accessor

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An impersonator-property accessor accepts a failure argument
in the same was as a structure-type--property accessor.
This commit is contained in:
Matthew Flatt 2017-12-22 18:17:45 -07:00
parent 8444b70bc1
commit fe1d9ee517
2 changed files with 8 additions and 2 deletions
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8
pkgs/racket-doc/scribblings/reference/chaperones.scrbl
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@ -1076,7 +1076,7 @@ given.
@defproc[(make-impersonator-property [name symbol?])
(values impersonator-property?
(-> any/c boolean?)
(-> impersonator? any))]{
(->* (impersonator?) (any/c) any))]{
Creates a new @tech{impersonator property} and returns three values:
@ -1095,7 +1095,11 @@ Creates a new @tech{impersonator property} and returns three values:
returns the value associated with an impersonator for the property;
if a value given to the accessor is not an impersonator or does not
have a value for the property (i.e. if the corresponding impersonator
property predicate returns @racket[#f]), the @exnraise[exn:fail:contract].}
property predicate returns @racket[#f]), then a second optional argument
to the selector determines its response: the @exnraise[exn:fail:contract]
is if a second argument is not provided, the second argument is tail-called
with zero arguments if it is a procedure, and the second argument is returned
otherwise.}
]}

2
pkgs/racket-test-core/tests/racket/chaperone.rktl
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@ -271,6 +271,8 @@
(exn-message exn))))
(err/rt-test (get1 v1) handler)
(test 'no get1 v1 'no)
(test 'no get1 v1 (lambda () 'no))
(err/rt-test (get1 v2) handler)
(err/rt-test (get1 v3) handler)
(err/rt-test (get1 v4) handler)