Remove autoload might break the straight-use-package-mode

[ccqpein]

I found the latest rust-mode cannot load successfully by my use-package (turned on the straight.el use-package integrated).

After some investigating, I found the PR #526 remove the ;;;###autoload of rust-mode. It causes straight-use-package cannot find the rust-mode function. (I guess it doesn't load the rust-mode.el when it initing?)

After more playing around, there are several behaviors were revealed.

1. if I (load "~/.emacs.d/straight/repos/rust-mode/rust-mode.el") in *scratch* buffer. I can call M-x rust-mode. But M-x straight-use-package cannot find the rust-mode
2. if I (autoload 'rust-mode "rust-mode" nil t) in *scratch* buffer. It does the same thing as 1..
3. If I load rust-mode.el in use-package :init step. It works fine. Furthermore, if I (setq rust-mode-treesitter-derive t) before in :init before loading, it will in treesitter mode as master branch code is designed to do.

I haven't raised up the solution of this issue. I guess it is the autoload is necessary for straight.el. I am going to report this to them.

[ccqpein]

Also raised the question to straight.el repo. link

[jroimartin]

Related: #528

[condy0919]

;; in rust-mode.el ...

;;;###autoload
(autoload 'rust-mode "rust-mode.el" nil t)

It will generate an (autoload 'rust-mode "rust-mode.el" nil t) in rust-mode-autoloads.el, but it looks like odd as of an autoload is autoloaded.

[psibi]

@ccqpein Can you check if this PR by @jroimartin fixes it for you: #530 ?

[ccqpein]

@psibi I just try and it fixes the rust-mode. Now my rust file can load the rust-mode (from rust-prog-mode.el). However, the straight-use-package still cannot find the rust-mode by M-x straight-use-package.

I might find sometime to study how the straight.el handle straight-use-package

[ccqpein]

Figure out it works. Thanks for @jroimartin 's PR