I think this may be a problem in macro expansion with submodules. The `#%module-begin` from `racket/base` adds a submodule declaration for `configure-runtime` when it doesn't see an existing submodule declaration for `configure-runtime` --- but it looks for an existing declaration as an immediate one, before macro-expanding the module body.
In your code, the `mute` wrapper hides the declaration of `configure-runtime`, so a conflicting one gets added. The tricky part is that this happens the second time that the `test` submodule is expanded: * The overall module's body is forced via `local-expand`. * As a part of that local expansion, the `test` submodule is expanded' its expansion includes a declaration of a `configure-runtime` submodule. * The overall module's expanded body is wrapped back in `#%module-begin`, which will re-expand all of the content, including the `test` submodule. * The `test` submodule this second time around has a `#%module-begin` that is supposed to be bound to `#%plain-module-begin`, but it ends up being captured[*] by `#%module-begin` from "bootstrap-lang.rkt", so that the submodule's body is again local-expanded and again send to `#%module-begin` from `racket/base` with a `mute` wrapper around the `configure-runtime` sub-submodule. The [*] step seems wrong to me. I think this may be an example of a problem deep in the macro expander, and solving that is my next project. Since the repair (assuming that I have correctly diagnosed the cause) may be a while, do you have a workaround already? The macro name `mute` suggests that you may want to suppress the printing of expression results at the top-level of a module, and that might be as easy as expanding `#%module-begin` to `#%plain-module-begin`. Or maybe `syntax/wrap-modbeg` can help, or maybe the strategy used by `syntax/wrap-modbeg` would work better for your macro. At Thu, 21 Aug 2014 17:22:29 +0100, Marco Monteiro wrote: > Hello! > > I'm using Racket 6.1 > > I'm trying to understand this error. I'm using submodules in a language I > defined. The language file is here: > > http://pastebin.com/7RiHHRmi > > Notice the commented out line 28. > > I use that language in the following code > > http://pastebin.com/Qa6RD9wF > > raco expanding this last file fails with > > module: duplicate submodule definition > at: configure-runtime > in: module > context...: > /usr/share/racket/pkgs/compiler-lib/compiler/commands/expand.rkt:29:11: > loop > /usr/share/racket/pkgs/compiler-lib/compiler/commands/expand.rkt: > [running body] > /usr/share/racket/collects/raco/raco.rkt: [running body] > /usr/share/racket/collects/raco/main.rkt: [running body] > > If I uncomment line 28 it no longer fails. If I use (module ...) instead of > (module* ...) it no longer fails independently of line 28 being commented > out or not. > > Trying to macro expand that in drracket gives me "Internal error: car: > contract violation ." error. > > What is happending here? > > Thanks, > Marco > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
