bug#28990: 27.0.50; thunk-delay: running expansion also requires lexical-binding

[Michael Heerdegen <michael_heerdegen@web.de>]

Hello,

having only lexical-binding: t in "thunk.el"'s header is not sufficient:
to make thunks work ok, `thunk-delay' needs lexical-binding when the
expansion is run.

Try e.g. something trivial as

#+begin_src emacs-lisp
(defun my-thunk-test ()
  (thunk-force (thunk-delay (+ 1 2))))
#+end_src

This compiles ok, but executing (my-thunk-test) without lexbind enabled
gives you a meaningless error like "void-variable: forced".

I think we should document (in the file header) that lexical-binding
mode is required when thunks are created with `thunk-delay'.  I think we
could additionally raise an error in the expansion of `thunk-delay' when
lexical-binding -> nil.


TIA,

Michael.




In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.24)
 of 2017-10-25 built on drachen
Repository revision: cb73c70180f57f3fb99fae3aaefbacf0a61cea3f
Windowing system distributor 'The X.Org Foundation', version 11.0.11905000
System Description:	Debian GNU/Linux testing (buster)