[racket-dev] Constructing an identifier to an unexported binding

Right, but why cannot we forge an identifier easily? I'm happy getting
an armed identifier. What are the reasons for preventing such a
construction?

On Thu, May 23, 2013 at 6:04 PM, Carl Eastlund <cce at ccs.neu.edu> wrote:
> Essentially yes.  It doesn't do anything else, but it needs an identifier to
> do it.  Currently, TR starts with a module and a symbol, goes through an
> expensive process to forge an identifier from them, just to call
> free-identifier=? to compare based on the module and the symbol after all.
> Doing the comparison directly, without ever forging the identifier, would be
> quicker.
>
>
> On Thu, May 23, 2013 at 8:43 PM, Eric Dobson <eric.n.dobson at gmail.com>
> wrote:
>>
>> Isn't that exactly what free-indentifier=? is checking for on
>> identfiers with a module level binding? Or is there something else it
>> does?
>>
>> On Thu, May 23, 2013 at 3:13 PM, Carl Eastlund <cce at ccs.neu.edu> wrote:
>> > On Thu, May 23, 2013 at 4:13 PM, Ryan Culpepper <ryanc at ccs.neu.edu>
>> > wrote:
>> >>
>> >> On 05/23/2013 01:57 AM, Eric Dobson wrote:
>> >>>
>> >>> Some modules have macros which expand into identifiers that are not
>> >>> exported, as they want to protect those bindings. TR currently has the
>> >>> following code which allows it to generate an identifier which is
>> >>> free-identifier=? to what would appear in the output of the macros.
>> >>>
>> >>> define (make-template-identifier what where)
>> >>>    (let ([name (module-path-index-resolve (module-path-index-join
>> >>> where
>> >>> #f))])
>> >>>      (parameterize ([current-namespace (make-empty-namespace)])
>> >>>        (namespace-attach-module (current-namespace) ''#%kernel)
>> >>>        (parameterize ([current-module-declare-name name])
>> >>>          (eval `(,#'module any '#%kernel
>> >>>                   (#%provide ,what)
>> >>>                   (define-values (,what) #f))))
>> >>>        (namespace-require `(for-template ,name))
>> >>>        (namespace-syntax-introduce (datum->syntax #f what)))))
>> >>>
>> >>> This turns out to be a slightly slow part of the initialization of TR.
>> >>> Does anyone know another way to get such an identifier?
>> >>
>> >>
>> >> There's another way around this issue, which is to avoid creating these
>> >> identifiers at all. In other words, change the representation of the
>> >> type
>> >> environment to something that supports symbol+module pairs as keys in
>> >> addition to identifiers. The easiest way to do that is to add in a hash
>> >> table behind the current free-id-table, since the two tables would
>> >> handle
>> >> disjoint sets of identifiers.
>> >>
>> >> Ryan
>> >
>> >
>> > I would not have thought that'd work, but apparently identifier-binding
>> > will
>> > give one that information.  Nice going, Ryan!
>> >
>> > --Carl
>>
>