[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Byte-compiler warnings
From: |
Stefan Monnier |
Subject: |
Re: Byte-compiler warnings |
Date: |
Wed, 24 Jun 2015 23:06:40 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) |
> One question is: if (goto-char (point-min)) is
> equivalent, why cannot the byte-compiler just use that
> instead for the compiled version?
In general such "use <foo> instead" messages are used instead of doing
the rewrite silently for two reasons:
1- the two aren't actually equivalent. The provide the same feature but
in different ways or with different corner case behavior, so the compiler
can't safely replace one for the other. E.g. beginning-of-buffer
sets the mark; which is the reason why it's usually not what you want
from Elisp, but the compiler can't know if that's actually what you want.
2- the two are equivalent, but one is deprecated so we want people to
fix the source code. This might be also because the compiler can
detect and optimize some cases but not all, so it's important to tell
the programmer that these forms are deprecated so she can hopefully
stop using them also in those places that the byte-compiler can't
detect (e.g. '(lambda ...) vs #'(lambda ...) which then compiler can
detect when passed to `apply' or `mapcar' but not in general since in
general '(lambda ...) might just be a list rather than a function).
Stefan