Gnome-shell segfault: "Can't init class Variant"

[Amy C <mathematical coffee gmail com>]

Hi all,

All of a sudden a couple of days ago (4/Aug afternoon AEST) my
gnome-shell refused to start with the following error:

Exception was: Error: Failed to throw Exception 'Object 0xaf7065b0
proto 0xaf702078 doesn't have a dynamically-registered class, it has
$$`'
    lineNumber = '243'
    fileName = '"/usr/share/gjs-1.0/overrides/GLib.js"'
    stack = '"_init()@/usr/share/gjs-1.0/overrides/GLib.js:243"
@/usr/share/gnome-shell/js/ui/environment.js:3
"'
Can't init class Variant

Aborted

I have not managed to get it to start since, always getting the above
error (but the '$$`' appears to be random, sometimes rendering as odd
symbols).

I do not know what I would have done to trigger this. I have emptied
my ~/.local/share/gnome-shell/extensions so to eliminate them as a
problem. I can successfully log in to any other shell (including
'Classic GNOME with Compiz'), so this is gnome-shell specific.

Does anyone know how to fix this/what I can do to further diagnose the
problem? (that error message is the one in .xsession-errors and also
that appears in the terminal when I try a `gnome-shell --replace` from
there).

cheers (I miss gnome-shell already!)