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

> I think "the right way" would be for the `cl-flet` implementation to use
> a `cl--expand-flet` function returning which functions are used
> and which aren't.
>
> Then we could use it here without such duplication, *and* we could use
> it in `cl-flet` to emit warnings about unused functions.
>
> WDYT?

I agree.  I think the root of the problem is, ~cl-flet~ is generally not
implemented well.  Feels like it was implemented in a rush.

- (func exp) is non-standard and ad-hoc.  Do you happen to remember,
  maybe it was invented solely for ~cl--generic-lambda~?

- (func exp) definition form is described incorrectly in the docstring:
  it should be (FUNCTION-NAME SYMBOL) and so on; this also affects
  cl-macrolet docstring which claims it's “like cl-flet” but in fact
  it's not as it doesn't support this definition form

- ~cl-flet~ with invalid function names should error but it doesn't

I implemented ~cl--expand-flet~ but I felt simply returning a list of
used symbols would be just another ad-hoc addition so I decided to
instead add an interface to execute arbitrary code during
macroexpansion.  It took longer than I expected but I'm satisfied with
the result.  I'll open a standalone bug (my implementation happens to
fix some outstanding issues); when changes are (hopefully) merged, we'll
continue on with this one.

Quick reference: if all goes well, the definition of
~cl--generic-lambda~ is to become
#+begin_example emacs-lisp
..
(let* ((parsed-body (macroexp-parse-body body)) uses-cnm
       (cnm (make-symbol "cl--cnm"))
       (nmp (make-symbol "cl--nmp"))
       (nbody (cl--expand-flet macroenv (cdr parsed-body)
                (cl-call-next-method (push cnm uses-cnm) cnm)
                (cl-next-method-p (push nmp uses-cnm) nmp)))
       ;; FIXME: Optimize the case where call-next-method is
       ;; only called with explicit arguments.
       )
  ..)
#+end_example

This involves a “macro” version of expand-flet; we'll see whether it's
worth keeping alongside the corresponding function.

If you can, please confirm my suspicion that (FUNC EXP) definitions were
indeed invented solely for ~cl--generic-lambda~.