bug#60450: 30.0.50; Strange behavior of compiler macros in *scratch*

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> The doc string of cl-define-compiler-macro says
>   "This is like ‘defmacro’, but macro expansion occurs only if the call to
>  FUNC is compiled (i.e., not interpreted)."

`cl-define-compiler-macro` is built on top of the "new" ELisp compiler
macro feature.  I think that feature is documented vaguely (poorly?)
enough that it does allow expansion (or not) for interpreted code.

> C-j is bound to eval-print-last-sexp, which I wouldn't expect to compile
> anything, and its doc string doesn't mention anything AFAICS.  Not sure if
> that's a bug in the code or something missing in the docs.

Trying to distinguish those calls to `macroexpand-all` which come from
the compiler from those that come from elsewhere doesn't seem worth the
trouble, so I'd rather consider it as a doc bug.

The doc should also make it clear that contrary to `defmacro` there is
no guarantee that it will be called (nor *when* it's called).


        Stefan