At Wed, 10 Jul 2013 23:15:46 -0400, Ryan Culpepper wrote: > On 07/10/2013 09:04 PM, Asumu Takikawa wrote: > > Hi all, > > > > I'm currently trying to fix the Typed Racket unit tests. I think I've > > narrowed down the issue to a certain syntax property for keyword > > functions. > > > > The issue is illustrated by the following example: > > > > #lang racket > > > > (require racket/file > > (for-syntax racket/file > > racket/keyword-transform)) > > > > ;; the property is #f > > (begin-for-syntax > > (displayln > > (syntax-case (expand-syntax #'(copy-directory/files 1 2)) () > > [(let-values (((temp1) _) > > ((temp2) _)) > > (if _ > > (#%plain-app1 copy-directory/files15 e1 ...) > > (#%plain-app2 copy-directory/files17 e2 ...))) > > (syntax-procedure-converted-arguments-property > #'copy-directory/files15)]))) > > > > ;; property is syntax > > (begin-for-syntax > > (displayln > > (syntax-case (local-expand #'(copy-directory/files 1 2) 'expression > null) () > > [(let-values (((temp1) _) > > ((temp2) _)) > > (if _ > > (#%plain-app1 copy-directory/files15 e1 ...) > > (#%plain-app2 copy-directory/files17 e2 ...))) > > (syntax-procedure-converted-arguments-property > #'copy-directory/files15)]))) > > > > There are two syntax-time computations here. Both are expanding an > > application of a keyword function (one with local-expand, one with > > expand) and looking at the resulting syntax. > > > > The key point here is that I want to find the property looked up by > > `syntax-procedure-converted-arguments-property` on an output identifier > > because Typed Racket needs it to type-check the expansion. > > > > Unfortunately, as the comments indicate, only the second piece of code > > can find the property. The reason appears to be that the property key is > > actually a private `gensym`ed symbol and the two pieces of code appear > > to get separate instantiations of the kw.rkt module (perhaps at different > > phases). > > > > To check that, if I modify kw.rkt to use a plain symbol, both of the > > snippets above return the same property value. > > > > Anyone have any idea how I can keep using `expand` but still be able to > > look up the property? > > To get information about a phase-0 '#%app' expansion, you need to call > the phase-1 version of 'syntax-procedure-converted-arguments-property'. > That's going to require a bit of phase-crossing trickery, because the > identifier you want to query is a phase-0 (dynamic) value, and you want > the result as a phase-0 value, but the phase-1 function naturally > consumes and produces phase-1 values. > > One solution is to use 'quote-syntax', 'eval', and 'phase1-eval' all > together. Use 'eval' with 'quote-syntax' to convert the phase-0 > identifier to a phase-1 identifier. Use 'phase1-eval' to run the > computation at phase 1 and capture the phase-1 result as a phase-0 value > (also using 'quote-syntax').
I haven't thought about this much, but would it make more sense to move the property key to a cross-phase persistent module (with a `protected' provide) in this case? _________________________ Racket Developers list: http://lists.racket-lang.org/dev
