Re: pacifying "might not be defined at runtime" warning

[Stefan Monnier <monnier@iro.umontreal.ca>]

> "cd lisp; make compile-always" generates several "might not be defined at
> runtime" warnings in the master branch. For example, it generates the attached
> warnings in lisp/vc.

[ Note: when I say "vc.el" below, it includes generic VC
  files other than vc-hooks.el, such as vc-dispatch.el.  ]

The vc-<backend>.el files provide implementations for the functions used
in vc-hooks.el as well as for those used in vc.el.

In the parts that implement the vc.el functionality, it's "perfectly
safe" to call functions provided by vc.el, since they're supposed to
only be used *from* vc.el (i.e. when vc.el is already loaded).

> Is there some reason we shouldn't add directives like
> (require 'vc) to pacify the byte compiler here? (See the 2nd attachment.)

The reason is that vc-<backend>.el is autoloaded as soon as you visit
a file that's managed by <backend>, even if you never have and never
will use VC, so a (require 'vc) in those files would load VC
too eagerly.


        Stefan