[plt-dev] define-match-expander <-> unlib.plt doesn't compile

Unlib.plt doesn't compile, as you (Sam) reported several weeks ago. I  
tried to fix the problem, and started wondering whether the underlying  
problem was whether 'define-match-expander' was working incorrectly.   
For instance, what should this program produce?

foo.ss:

#lang scheme

(define-match-expander my-cons
   (error 'dontcare "aagh!")
   cons)

(provide (rename-out [my-cons cons]))

bar.ss:

#lang scheme

(require "foo.ss")

(cons 3 4)

Reading the docs, it looks like it should produce the pair containing  
3 and 4, but it actually signals the error. It appears to me that the  
untyped folks are (mis?)reading the docs in the same way I am.

Am I wrong, or is define-match-expander broken, or is something else  
going on?

Thanks,

John

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