Compiling a module that refers to a binding created by a use of local-expand in a 'module-begin context causes an unhelpful internal error

[lexi-lambda]

Here’s a Racket program:

#lang racket

(begin-for-syntax
  (local-expand
   #'(#%plain-module-begin
      (begin-for-syntax
        (define x 42)))
   'module-begin
   '()))

(begin-for-syntax
  (println x))

This program is arguably evil, I’m not sure, but whether it is or it isn’t, it currently fails with a pretty unhelpful error if you try to run it:

$ racket modbeg-effects.rkt
42
hash-ref: no value found for key
  key: 'x

Curiously, the error does not occur during expansion, since raco expand expands the module happily, without errors:

$ raco expand modbeg-effects.rkt
42
(module modbeg-effects racket
  (#%module-begin
   (module configure-runtime '#%kernel
     (#%module-begin (#%require racket/runtime-config) (#%app configure '#f)))
   (begin-for-syntax
    (#%app
     local-expand
     (quote-syntax (#%plain-module-begin (begin-for-syntax (define x 42))))
     'module-begin
     '()))
   (begin-for-syntax (#%app println x))))

However, the error is a compile-time error, not a runtime error, since it fails if the program is compiled with raco make:

$ raco make modbeg-effects.rkt
42
hash-ref: no value found for key
  key: 'x
  compilation context...:
   /private/tmp/modbeg-effects.rkt

[mflatt]

Thanks for the report!

[lexi-lambda]

Thank you for the fix!