bug#69120: Spurious "function is not known to be defined" if defined in `use-package` body

[Eli Zaretskii <eliz@gnu.org>]

> From: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> Date: Wed, 14 Feb 2024 14:16:09 +0300
> 
> I have many functions that are only useful inside a specific mode. So I
> group them with `use-package`, by defining them inside `:init` or
> `:config` section, depending on the use.
> 
> It turns out, byte-compiler does not consider such functions to be
> defined and prints a warning about it.
> 
> # Steps to reproduce (in terms of terminal commands)
> 
>     λ cat test.el
>     ;;; -*- lexical-binding: t -*-
>     (use-package prog-mode
>       :init
>       (defun hello()
>         (print "hello"))
>       (hello))
>     λ emacs -batch -f batch-byte-compile test.el
> 
>     In end of data:
>     test.el:6:4: Warning: the function ‘hello’ is not known to be defined.
> 
> ## Expected
> 
> File gets compiled with no warnings
> 
> ## Actual
> 
> There's a warning
> 
>     test.el:6:4: Warning: the function ‘hello’ is not known to be defined.

What do you get if you macro-expand your code?