From 727cd1ca9f90fd5e54cb23a49aa673debb225540 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sun, 7 Mar 2021 07:48:50 -0700
Subject: [PATCH] raco demod: report that it works only on BC

Closes #3706
---
 pkgs/compiler-lib/compiler/demodularizer/batch.rkt |  5 ++++-
 pkgs/racket-doc/scribblings/raco/demod.scrbl       | 11 ++++++-----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/pkgs/compiler-lib/compiler/demodularizer/batch.rkt b/pkgs/compiler-lib/compiler/demodularizer/batch.rkt
index 9d869b5481..464ba093c1 100644
--- a/pkgs/compiler-lib/compiler/demodularizer/batch.rkt
+++ b/pkgs/compiler-lib/compiler/demodularizer/batch.rkt
@@ -16,7 +16,10 @@
                  (garbage-collect-toplevels-enabled #t)]                         
                 [("-r" "--recompile") "Recompile final module to re-run optimizations"
                  (recompile-enabled #t)]                         
-                #:args (filename) 
+                #:args (filename)
+                (unless (eq? 'racket (system-type 'vm))
+                  (raise-user-error (format "~a: supported only on Racket BC"
+                                            (short-program+command-name))))
                 (demodularize filename (output-file))))
 
 (module test racket/base)
diff --git a/pkgs/racket-doc/scribblings/raco/demod.scrbl b/pkgs/racket-doc/scribblings/raco/demod.scrbl
index 0f82657449..6f18861bc4 100644
--- a/pkgs/racket-doc/scribblings/raco/demod.scrbl
+++ b/pkgs/racket-doc/scribblings/raco/demod.scrbl
@@ -3,10 +3,11 @@
 
 @title[#:tag "demod"]{@exec{raco demod}: Demodularizing Programs}
 
-The @exec{raco demod} command takes a Racket module and flattens
-all of its dependencies into a single compiled module. 
-A file @filepath{@nonterm{name}.rkt} is demodularized into 
+The @exec{raco demod} command, which works only for Racket @tech[#:doc
+guide-doc]{BC}, takes a Racket module and flattens all of its
+dependencies into a single compiled module. A file
+@filepath{@nonterm{name}.rkt} is demodularized into
 @filepath{@nonterm{name}_rkt_merged.zo}.
 
-The demodularized zo file can be run by passing it as an argument to
-the @exec{racket} command-line program.
+The demodularized @filepath{.zo} file can be run by passing it as an
+argument to the @exec{racket} command-line program.