[Bug-kawa] [bug #37051] define-syntax does not work when included

[Per Bothner]

Update of bug #37051 (project kawa):

                  Status:                    None => Invalid                

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Follow-up Comment #4:

Thanks for the test-case.  I believe the compiler is correct.
The call to bar should *not* match the define, because of macros hygiene:

http://en.wikipedia.org/wiki/Hygienic_macro
http://www.randomhacks.net/articles/2002/09/13/hygienic-macros

The reason it "works" when you remove the begin is because then things happen
at the "top-level" which has special rules.

One solution is to explicitly pass bar as a macro argument:

(begin
(define-syntax foo
  (syntax-rules ()
    ((_ e bname) (define (bname) (display e)(newline)))))
(foo 123 bar)
(bar)
)

Another is to use define-syntax-case, and a "literal" 'bar is the expansion:

(begin
(define-syntax-case foo ()
  ((_ e) #`(define (#,'bar) (display e)(newline))))
(foo 123)
(bar)
)

Even better would be to use datum->syntax:

(begin
(define-syntax-case foo ()
  ((foo e) #`(define (#,(datum->syntax #'foo 'bar)) (display e)(newline))))
(foo 123)
(bar)
)

The datum->syntax means to take the symbol 'bar and convert it to a syntax
object in the same lexical scope as foo.  (For this to work you need to use
(foo e) in the pattern.)




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