bug#66136: 29.1; byte-compiler reports "misplaced interactive spec" with empty fct in lexical environment

["Mattias Engdegård" <mattias.engdegard@gmail.com>]

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22 sep. 2023 kl. 23.39 skrev Stefan Monnier <monnier@iro.umontreal.ca>:

> I know Mattias played with this part of the code (mostly to try and
> figure what to do about the ordering of the various possible kinds of
> declarations, which is a related yet different issue).  Maybe he has
> a more informed opinion.

Can't lay much claim to that I'm afraid. In this case I'd just have macroexp-parse-body return an empty body and be done with it. Suggested patch attached.

Our triptych of meta-forms in function bodies (documentation, declare, interactive) is still not handled in a very principled or robust way. We keep parsing and re-parsing them in several places. I'm tempted to replace lambda with an intermediate form where these things are already parsed, early in the front-end (maybe even macroexpand-all).

There are all sorts of little annoyances, such as:

- if nothing comes after a (literal) doc string, the doc string also becomes the function body
- `declare` is only allowed in named definitions because it is macro-expanded very early, so we have no way of annotating lambda expressions
- not sure :documentation is handled correctly everywhere since it's a late addition
- that 'misplaced interactive spec' warning shouldn't be emitted from the Lisp optimiser at all but fully handled in the front-end like all syntax errors


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diff --git a/lisp/emacs-lisp/macroexp.el b/lisp/emacs-lisp/macroexp.el
index f96e0d74026..3bf0222c40d 100644
--- a/lisp/emacs-lisp/macroexp.el
+++ b/lisp/emacs-lisp/macroexp.el
@@ -525,12 +525,15 @@ macroexpand--all-toplevel
 (defun macroexp-parse-body (body)
   "Parse a function BODY into (DECLARATIONS . EXPS)."
   (let ((decls ()))
-    (while (and (cdr body)
+    (while (and body
                 (let ((e (car body)))
                   (or (stringp e)
                       (memq (car-safe e)
                             '(:documentation declare interactive cl-declare)))))
       (push (pop body) decls))
+    (when (and (null body) (stringp (car decls)))
+      ;; No body but a literal doc string: move it back to the body.
+      (push (pop decls) body))
     (cons (nreverse decls) body)))
 
 (defun macroexp-progn (exps)