I am getting strange error in my Racquel package unit tests. I'm not sure what
Racket release it started appearing in, but certainly 6.6 or 6.5. A couple of
days ago, I posted the all of code that was causing the error, but there was
too much going on for anyone to make sense of it (including me) and so I
deleted the post. Now I've spent a few hours and reduced the bug to the minimum
code required to reproduce it.
The error I'm seeing in my tests is:
define-values: assignment disallowed
cannot re-define a constant
constant: lifted.0
This error is rather obtuse and I have no I idea what it trying to communicate
given that the code in question has no constant named "lifted". I can only
assume that it is some internal error related to syntax lifting.
Below are the two modules needed to reproduce the error. What makes this error
particularly strange is that the error occurs until the foobar function in
bug2.rkt is commented out. This function is not even called anywhere!
Interestingly it must call query-rows. If foobar calls anything else, the bug
goes away. This may mean that there is an error somewhere in the db package.
When the foobar function is commented out, everything works fine. In this
example, for the sake of brevity, it will give an error that error-me% is
undefined. I could have defined it and the other classes, and it would have ran
with no errors.
The problem is that in the real version of the code, the foobar function is
used and necessary. I can't just comment it out. Until I know what's going on
here, I can't even devise a workaround.
bug.rkt:
#lang racket
(require "bug2.rkt" (for-syntax racket/syntax syntax/parse "bug2.rkt"))
(define-syntax (data-class stx)
(syntax-parse stx
[(_ base-cls:id (i-face:id ...) elem:data-class-element ...)
(with-syntax ([m-data (generate-temporary)])
#'(let* ([m-data (new error-me%)])
(class* base-cls (bar% i-face ...)
elem.cls-expr ...
(inspect #f))))]))
(define (gen-data-class)
(let* ([cls-nm 'cls-nm]
[stx #`(data-class object% (foo%) (super-new))])
(eval-syntax stx bug-namespace)))
(define fred% (gen-data-class))
bug2.rkt:
#lang racket
(require syntax/parse db (for-syntax racket/syntax syntax/parse))
(provide (all-defined-out))
;;; Until this is commented-out the error persists.
(define (foobar con) (query-rows con ""))
(define-namespace-anchor bug-namespace-anchor)
(define bug-namespace (namespace-anchor->namespace bug-namespace-anchor))
(define-syntax-class data-class-element
#:attributes (cls-expr)
(pattern (x:expr ...)
#:attr cls-expr #'(x ...)))
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