Subject: 24.5; Opening output file: invalid argument, .../foo-<-4-n.el

From: Drew Adams <[email-masked]>
Date: Fri, 10 Jun 2016 10:35:54 -0700 (PDT)

emacs -Q

C-x C-f foo-<-4-n.el

Type some text in that file buffer.

C-x C-s  ; try to save it.

Saving file d:/usr/drew/drews-lisp-20/foo-<-4-n.el...
basic-save-buffer-2: Opening output file: invalid argument, d:/.../foo-<-4-n.el

Apparently it doesn't like `<' in a file name?  If so, and if that is
"normal", then the user should get a much better error message than
this.

(Same problem in the latest Emacs 25 build I have.)

In GNU Emacs 24.5.1 (i686-pc-mingw32)
 of 2015-04-11 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/usr --host=i686-pc-mingw32'