GNU bug report logs - #46834
28.0.50; byte-compiling the standard counter closure fails

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Pip Cet <pipcet <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.0.50; byte-compiling the standard counter closure fails
Date: Sun, 28 Feb 2021 15:04:06 +0000

(My apologies if this is well-known, documented, or plain stupid on my
part, but I think it's an interesting gotcha. Feel free to close
immediately in those cases.)

Steps to reproduce from emacs -Q:
Evaluate the following in a lexically-bound Emacs Lisp buffer:

(byte-compile (let ((l 0)) (lambda () (cl-incf l))))

Expected result:

A byte code object which will increment its return value by one every
time it is called.

Actual result:

A byte code object which always returns 1.

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