From: Taylor R Campbell <campbell@mumble.net>
Date: Mon, 14 Jan 2019 07:44:05 +0000 (+0000)
Subject: Report bad expressions more clearly.
X-Git-Tag: mit-scheme-pucked-10.1.20~11^2~66^2~94
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=deffa305690e6581f788016b579dfbed87a0f0e6;p=mit-scheme.git

Report bad expressions more clearly.
---

diff --git a/src/compiler/back/bitutl.scm b/src/compiler/back/bitutl.scm
index 98e6502ae..7cb117b05 100644
--- a/src/compiler/back/bitutl.scm
+++ b/src/compiler/back/bitutl.scm
@@ -100,6 +100,10 @@ USA.
 (define (evaluate expression pc-value)
   (define (inner exp)
     (cond ((pair? exp)
+	   (if (not (and (pair? (cdr exp))
+			 (pair? (cddr exp))
+			 (null? (cdddr exp))))
+	       (error "evaluate: bad expression:" exp))
 	   ((find-operator (car exp))
 	    (inner (cadr exp))
 	    (inner (caddr exp))))