Report bad expressions more clearly.

diff --git a/src/compiler/back/bitutl.scm b/src/compiler/back/bitutl.scm
index 98e6502ae706ef388ed567902ae150bdbda9b5c0..7cb117b05d55b5b5b42b15fcfc801e6e25e699e1 100644 (file)
--- 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))))