Yes, this difference in the way that v5.3 and v5.2.1 handle binding was
intended, though it was explained well in the change log.
Your code includes
#`#,me-name
where the value of `me-name' is a symbol. In both v5.2.1 and v5.3, as
`me-name' is coerced to an identifier (i.e., a syntax object), it gets
its lexical context from the enclosing environment, which is the
"auto-req-lang.rkt" module.
When you inject the identifier into the macro-expansion result as a
`require' path, the `require'd identifiers should only bind identifiers
that have the same context --- that is, other identifiers whose context
is "auto-req-lang.rkt". That's what happens in v5.3, at least. The
identifiers in "example.rkt" don't have that context, and so they don't
get bound.
Identifiers in "example.rkt" did get bound by the `require' in v5.2.1,
because the macro system didn't correctly track module-level context.
It turns out that some natural uses of submodules exposed this
bug/weakness of the macro expander, and so we fixed it. I'm sorry for
the subtle backward incompatibility, though.
Instead of
(syntax-local-introduce #`#,me-name)
I think you probably want
(datum->syntax stx me-name)
which should work the same in v5.2.1 and v5.3.
At Wed, 8 Aug 2012 17:32:52 -0300, Gustavo Massaccesi wrote:
> Hi!
>
> I'm upgrading from version 5.2.1 to version 5.3 and I found a problem.
>
> The idea is that the module "auto-req-lang.rkt" is like racket/base,
> but when it is used as a language, it is automatically required
> for-syntax. (The name is extracted automatically.) The original file
> is much longer, but this is a minimal example that shows the
> difference between the Racket versions.
>
> In this case, the following "example.rkt" program works in 5.2.1 but
> fails in 5.3
>
> ; version 5.2.1 ==> #f
>
> ; version 5.3 ==> Error: syntax: unbound identifier in the
> transformer environment;
> also, no #%app syntax transformer is bound in: syntax
>
> Gustavo
>
>
> ;=== file: "auto-req-lang.rkt"
> #lang racket/base
> (require (for-syntax racket/base))
> (provide (except-out (all-from-out racket/base) #%module-begin))
> (provide (rename-out (module-begin #%module-begin)))
>
> {define-syntax (module-begin stx)
> (syntax-case stx ()
> [(module-begin body ...)
> (let-values ([(me-name ??) (module-path-index-split (car
> (identifier-binding #'module-begin)))])
> (with-syntax ([module-id (syntax-local-introduce #`#,me-name)])
> #`(#%plain-module-begin
> (require (for-syntax module-id))
> body ...
> )))])}
>
> ;=== end file: "auto-req-lang.rkt"
>
>
> ;=== file: "example.rkt"
> #lang s-exp "auto-req-lang.rkt"
>
> {define-syntax (just#f stx)
> (syntax #f)}
>
> (display (just#f))
>
> ;=== file: "example.rkt"
> ____________________
> Racket Users list:
> http://lists.racket-lang.org/users
____________________
Racket Users list:
http://lists.racket-lang.org/users
