bug#24122: Fix byte-compile of interactive closures

[npostavs]

Severity: minor
tags: patch
found: 24.3
found: 25.1

Running

    emacs -Q -l bug-byte-compile.el

gives

    bug-byte-compile.el:Warning: misplaced interactive spec: ‘(interactive)’

where bug-byte-compile.el is

;;; -*- lexical-binding: t -*-

(let ((foo--var nil))
  (defun foo ()
    (interactive)
    foo--var))

(byte-compile 'foo)

The problem is that byte-compile--reify-function which puts the bindings
inside the closure bindings inside the function body as an optimization,
puts them in front of the docstring and (interactive ...) form.  Here is
a fix:

>From 46cf05f447a7c834789c5ce8805cb5997c685c43 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Sun, 31 Jul 2016 20:46:37 -0400
Subject: [PATCH v1] Fix byte-compile of interactive closures

* lisp/emacs-lisp/bytecomp.el (byte-compile--reify-function): Put
bindings after docstring and `interactive' form, if any.
---
 lisp/emacs-lisp/bytecomp.el | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index dc7574e..175690a 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -2582,7 +2582,13 @@ byte-compile--reify-function
   (pcase-let* (((or (and `(lambda ,args . ,body) (let env nil))
                     `(closure ,env ,args . ,body))
                 fun)
+               (preamble nil)
                (renv ()))
+    ;; Split docstring and `interactive' form from body.
+    (when (stringp (car body))
+      (push (pop body) preamble))
+    (when (eq (car-safe (car body)) 'interactive)
+      (push (pop body) preamble))
     ;; Turn the function's closed vars (if any) into local let bindings.
     (dolist (binding env)
       (cond
@@ -2595,8 +2601,8 @@ byte-compile--reify-function
        ((eq binding t))
        (t (push `(defvar ,binding) body))))
     (if (null renv)
-        `(lambda ,args ,@body)
-      `(lambda ,args (let ,(nreverse renv) ,@body)))))
+        `(lambda ,args ,@preamble ,@body)
+      `(lambda ,args ,@preamble (let ,(nreverse renv) ,@body)))))
 
 ;;;###autoload
 (defun byte-compile (form)
-- 
2.8.0