Another follow-up from yesterday's doc reviews

[Eric Timmons]

On Thu, Sep 22, 2016 at 3:04 PM, Robert Goldman <rpgoldman at sift.net> wrote:
> It would be trivial to bind a special variable around the body of
> LOAD-ASD, and put something in DEFSYSTEM that will raise an INTELLIGIBLE
> error if that variable is not so bound
>
> (error "Do not load an ASDF system definition outside of ASDF:LOAD-ASD")

As I understand it, the issue isn't really with the DEFSYSTEM form
itself. Instead, the issue is with all the *other* code that could be
in the .asd file as the manual states that symbols from CL, ASDF, and
UIOP will all be available inside an .asd file without an IN-PACKAGE
form.

EVAL'ing a DEFSYSTEM form seems like a totally reasonable thing to do
outside the context that LOAD-ASD sets up. And actually, ASDF itself
does EVAL DEFSYSTEM forms, in package-inferred-system.lisp at the very
least.

-Eric