Removing program-arities export

Hello,

I am working on a patch for a bug I recently found in guile. The `program-arities` function is exported from the `(system vm program)` module and documented in the manual, but it is no longer defined (it was removed in commit 1c33be992e8120abd20add8021e4d91d226f5b6a).  It is only used in the `program-arity function`, which is not called anywhere in the Guile repository (and calling it with valid inputs results in an error due to the `program-arities` being undefined). See the shell session at the end of this email for details.

Removing those functions is simple, but the `arity:` accessors have more users, and since they're just pattern-matching on a list I'm concerned that they have been used for the new functions (eg, find-program-arity) so I'm not sure if it's safe to just remove them. In particular, `arity->arguments-alist` uses them unconditionally. However, `arity->arguments-alist` only has two callers, `program-arguments-alist` and `program-arguments-alists` (that's not a typo, the second one is pluralized), which call it conditionally. The conditions are different but both require that the given code passes the `primitive-code?` predicate. These functions are called from a few different places so it'll take a little more time to figure out if it's safe to remove them (or possibly just remove the logic conditioned by `primitive-code?`, if that is no longer in use, and leaving the rest of the function intact).

In solidarity,
Skyler

user@foreign-guix /d/shm> cat channels.scm
%default-channels

user@foreign-guix /d/shm> guix time-machine --channels=./channels.scm -- shell --container --nesting guile-next guile-readline
user@foreign-guix /dev/shm [env]$ guix describe
  guix 4a4a8c9
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 4a4a8c9d2621d4871c4b9c8857bfb0e6e53d7e56

user@foreign-guix /dev/shm [env]$ guile -q
GNU Guile 3.0.9-0.3b76a30
Copyright (C) 1995-2024 Free Software Foundation, Inc.
                                                                                                              
Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.
                                                                                   
Enter `,help' for help.
scheme@(guile-user)> (module-variable (resolve-module '(system vm program)) 'program-arities)
$1 = #<variable 734b7c40e940 value: #<undefined>>

scheme@(guile-user)> (use-modules (system vm program))
scheme@(guile-user)> (program-arity car #f)
ice-9/boot-9.scm:1676:22: In procedure raise-exception:
Unbound variable: program-arities

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.