From e97a2debe1b4c71190533fb2d76e7ceb59a3b07d Mon Sep 17 00:00:00 2001
From: Daphne Preston-Kendal <git@dpk.io>
Date: Thu, 30 Dec 2021 00:10:46 +0100
Subject: [PATCH] Friendlier error message for misuse of standard macros

---
 lib/init-7.scm | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/init-7.scm b/lib/init-7.scm
index 8a3ea91f..a8c88a74 100644
--- a/lib/init-7.scm
+++ b/lib/init-7.scm
@@ -143,13 +143,21 @@
     (lambda (expr use-env mac-env)
       (f expr mac-env))))
 
-(define er-macro-transformer
+(define er-macro-transformer*
   (lambda (f)
     (lambda (expr use-env mac-env)
       (f expr
          (make-renamer mac-env)
          (lambda (x y) (identifier=? use-env x use-env y))))))
 
+(define er-macro-transformer
+  (lambda (f)
+    (er-macro-transformer*
+     (lambda (expr rename compare)
+       (if (not (pair? expr))
+           (error "invalid use of non-identifier macro outside operator postion" expr)
+           (f expr rename compare))))))
+
 (define-syntax cond
   (er-macro-transformer
    (lambda (expr rename compare)