Consider this program

 const Gio = imports.gi.Gio;
 var themed_icon = new Gio.ThemedIcon ({names: ["name1", "name2"]});
 print ("icon: " + themed_icon);

This fails with the output in [1]. I tried this gjs and it seems to work fine there.

PS. I'm not so much interested in constructing an icon - GThemedIcon is just an example. It's more that I have a class I wrote myself that takes a GStrv as a construct property and I'd like that to work with seed.

[1] :

$ seed strv-property-example.js 

(seed:25519): GLib-GObject-CRITICAL **: g_value_transform: assertion `G_IS_VALUE (src_value)' failed

(seed:25519): GLib-GIO-CRITICAL **: g_themed_icon_constructed: assertion `themed->names != NULL && themed->names[0] != NULL' failed

(seed:25519): GLib-GObject-CRITICAL **: g_value_unset: assertion `G_IS_VALUE (value)' failed
icon: [object GThemedIcon]