Re: esup byte compile warnings

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Consider the following defun:
>
>  (defun esup-total-exec-time (results)
>    "Calculate the total execution time of RESULTS."
>    (cl-loop for result in results
>             sum (slot-value result 'exec-time) into total-exec-time
>             finally return total-exec-time))
>
> This produces a waring:
>
>  In esup-total-exec-time:
>  esup.el:166:52: Warning: Unknown slot ‘exec-time’

This warning means that the bytecompiler has not seen any `defclass`
that defines a slot `exec-time`.  Maybe it's perfectly normal (you know
that the object will indeed have an `exec-time` slot when that code will
be executed), e.g. because the object will be created in another file
which is not `require`d in this file, but without knowing more about
this slot it's hard to tell what's the best way to address the warning.

[...looking at https://github.com/jschaf/esup...]

Oh, I think it's because of

    (let ((load-path (append load-path (list esup-load-path))))
      (require 'esup-child))

which means that the `require` won't be executed by the byte-compiler
(because it's within a `let`).  Either you should just drop this
`load-path` trickery (and push the responsability of `load-path`
manipulation to the code that byte-compiles the files, as usual), or you
may want to wrap this within an `eval-and-compile`.

> Looks like the reason is that the byte-compiler unable to match
> ‘result’ with the class declaration.

The compiler doesn't even try to infer types.  It only checks that some
class somewhere has defined a slot of that name (that's good enough to
catch most typos).


        Stefan


PS: While I'm here I noticed:

    (eval-when-compile
      (if (and (<= emacs-major-version 24)
               (<= emacs-minor-version 3))
          (require 'cl)
        (require 'cl-lib)))

which makes no sense: those two libraries provide the same *kind* of
functionality, but under completely different names.  The rest of the
code uses things like `cl-loop`, so you need to (require 'cl-lib)
because that's what the code uses.  In Emacs<24.4, `cl-lib` will itself
load `cl` (because it uses it internally, but that's an implementation
detail).