Re: Cleaning up code

[Michael Albinus <michael.albinus@gmx.de>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> However, setting `byte-compile-force-lexical-warnings' to t is too
>> coarse. For example, Tramp's macro `with-parsed-tramp-file-name'
>> let-binds several variables "just in case". They are reported as unused
>> then, on every invocation of that macro.
>
> Yup, that's one of the main problems: when a single let in the source
> ends up duplicated after expansion so some expansions may use it while
> others end up not using it.
>
> We need to add some way to tell Emacs that it should check "the sum of
> all uses" or something like that.  In your case, this "sum" is
> open-ended, so we should instead just tell it not to check at all.

Yep.

There is also another case where it doesn't work as expected. Often, I
let bind a variable for side effect, like this:

      (let ((default-directory (tramp-compat-temporary-file-directory))
            (outline-regexp tramp-debug-outline-regexp))
        (outline-mode))

And I get from the byte compiler

tramp.el:1400:1:Warning: Unused lexical variable `outline-regexp'

In Tramp, there are many such stanzas of intended side effect
bindings. Therefore, there are too many false positives, that I could
see the real warnings I should fix.

Could we have a byte-compiler option telling that such bindings are
intended? Something like this:

      (let ((byte-compile-force-lexical-warnings nil)
            (default-directory (tramp-compat-temporary-file-directory))
            (outline-regexp tramp-debug-outline-regexp))
        (outline-mode))

>         Stefan

Best regards, Michael.