bug#2681: 23.0.91; incorrect line shown by lisp compiler

When I byte compile this file:
---~/temp.el------------------------------------------------
(defun test (vec)
  (cond	((= (length vec) 0)
	 (message "LEN=0"))
	((= (length vec) 1)
	 (message "LEN=1"))
	((= (length vec 2))
	 (message "LEN=2"))))
------------------------------------------------------------
The *Compile-Log* buffer shows these warnings:

Compiling file /home/handa/temp.el at Mon Mar 16 13:12:33 2009

In test:
temp.el:4:11:Warning: `=' called with 1 arg, but requires 2
temp.el:4:14:Warning: `length' called with 2 args, but requires 1

But the bug is on 6th line, not the 4th line.

---
Kenichi Handa
[email protected]