bug#24266: 25.1.50: Major mode set on line 1 cannot be changed.

[Alan Mackenzie]

Hello, Emacs.

Create a file which sets the mode in line 1, e.g.:

    /* -*- Mode: C -*- */

.  Start emacs -Q, then visit that file with C-x C-f.  It's major mode
is C Mode.

Now try, successively, M-x fundamental-mode, M-x c++-mode.  The major
mode stays C Mode in both cases.  This is a bug.

Note: the bug was introduced by patch

    commit 25f455815bfaa868dc470d445413df9a7a546c46
    Author: Alan Mackenzie <acm@muc.de>
    Date:   Thu May 5 11:05:49 2016 +0000

    Call hack-local-variables from major modes rather than from file visiting

    This prevents file/directory local variables from being lost when the major
    mode is set or changed.

It's cause was an inaccuracy in the doc string for
`hack-local-variables-prop-line'.

A patch is available and will be committed soon.

-- 
Alan Mackenzie (Nuremberg, Germany).