Feature request: let :autoloads, :commands, :functions declare symbols for other packages

[heraplem]

I often run into situations where package B depends on a symbol from package A.

Usually, it is enough to make sure that the use-package form for package A occurs before the use-package form for package B. It would be nice, though, to be able to decouple the init-file layout from the dependency order of the use-package stanzas.

But the real problem comes if the byte-compiler can't see a needed function symbol from package A. In this case, I have to add a :functions, :commands, etc. to the use-package form for package A. Now the use-package form for package A has to "know" about the fact that another use-package form is going to depend on that symbol, which is less than ideal.

The alternative, of course, is to simply use define-function, etc. as needed, but that also seems less than ideal.

The solution I'm envisioning is to make it so that keywords that declare function symbols can additionally take, for each symbol, the name of the package that that symbol is from, with a syntax similar to :hook.

(use-package c
  :functions (a-foo . a)
             ((b-bar b-baz) . b)
  :config
  (setq c-xxx (+ (a-foo) (b-bar) (b-baz))))

(use-package a)
(use-package b)