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bug#15786: 24.3; No warning on mal-formed let form when lexical-binding
From: |
Nathan Trapuzzano |
Subject: |
bug#15786: 24.3; No warning on mal-formed let form when lexical-binding |
Date: |
Sat, 02 Nov 2013 10:14:35 -0400 |
User-agent: |
Gnus/5.130007 (Ma Gnus v0.7) Emacs/24.3.50 (gnu/linux) |
Leo Liu <sdl.web@gmail.com> writes:
> Due to a typo in my code, I got a bug report on ggtags
> https://github.com/leoliu/ggtags/issues/17. I was fooled by the elisp
> compiler which warns mal-formed let forms without lexical-binding.
>
> To reproduce
> 1. Download the file in the attachment
> 2. byte-compile it
> 3. remove the first line and byte-compile it
>
> step 2 produces no warnings while step 3 does.
Under lexical binding, the malformed `let' is correctly reformed in
`cconv-convert' before it gets passed to the optimizer. In other words,
it's assumed to be properly formed. This looks like a bug.
On first thought, it seems that cconv-convert should check for proper
form and signal an _error_ if the check fails. On the other hand, this
would be inconsistent with what happens under dynamic binding. (On that
note, under dynamic binding, why is this considered a warning and not an
error?)
Patch attached.
>From 1cce762e1586ce9faa7fc41712973e22c1ea723c Mon Sep 17 00:00:00 2001
From: Nathan Trapuzzano <nbtrap@nbtrap.com>
Date: Sat, 2 Nov 2013 10:12:35 -0400
Subject: [PATCH] Assert proper form of let binding during byte compilation
under lexical binding.
---
lisp/emacs-lisp/cconv.el | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/lisp/emacs-lisp/cconv.el b/lisp/emacs-lisp/cconv.el
index f24e503..6d87521 100644
--- a/lisp/emacs-lisp/cconv.el
+++ b/lisp/emacs-lisp/cconv.el
@@ -289,12 +289,14 @@ places where they originally did not directly appear."
(dolist (binder binders)
(let* ((value nil)
- (var (if (not (consp binder))
- (prog1 binder (setq binder (list binder)))
- (setq value (cadr binder))
- (car binder)))
- (new-val
- (cond
+ (var (if (not (consp binder))
+ (prog1 binder (setq binder (list binder)))
+ (cl-assert (= (length (cdr binder)) 1) nil
+ "malformed let binding: `%s'"
(prin1-to-string binder))
+ (setq value (cadr binder))
+ (car binder)))
+ (new-val
+ (cond
;; Check if var is a candidate for lambda lifting.
((and (member (cons binder form) cconv-lambda-candidates)
(progn
--
1.8.4.2