I've pushed a repair for this bug. Ryan (thanks!) was exactly right about the cause.
At Fri, 13 Sep 2013 00:21:07 +0200, Tero Hasu wrote: > Ah, okay. Thanks Ryan. > > So it looks like the exact same phase-2 x binding is being introduced > twice, first during local-expand, and then during processing of the > expanded code, which causes a conflict. (And that something is being > done to prevent that for phase 0 and 1 bindings.) Fortunately this is > the sort of problem that I'm unlikely to soon run into in practical > code, I should think. Was just doing some testing. > > I conclude that long as I avoid top-level phase 2+ bindings, and I > guess beware of duplication of top-level phase 1+ side-effecting > operations, I should be okay with this approach. > > > On 12/09/13 22:16, Ryan Culpepper wrote: > > > Note that the problem is not restricted to submodules, and it has > > nothing to do with the fact that x is defined in two phases. The same > > error is raised by this program: > > > > #lang racket/load > > > > (module le-lang racket > > (provide > > (except-out (all-from-out racket) #%module-begin) > > (rename-out [module-begin #%module-begin])) > > > > (define-syntax (module-begin stx) > > (syntax-case stx () > > ((_ . bs) > > (local-expand > > #'(#%module-begin . bs) > > 'module-begin null))))) > > > > (module le-module 'le-lang > > (require (for-meta 2 racket/base)) > > (define x 0) > > (begin-for-syntax > > (begin-for-syntax > > (define y 2)))) > > > > I conjecture that maybe the problem is that the module's environment (or > > renames?) is not being cleared/reset at all phases when 'local-expand' > > returns, only phases 0 and 1. But in a brief search of the expander code > > I wasn't able to confirm my guess. > > > > Ryan > > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
