Created attachment 167132 [details]
Small test library displaying the bug behavior

Overview:

    When calling a function which returns a GParamSpec, gjs complains saying it can't create a JavaScript object for it.

Steps to Reproduce:

    The samplelib.tar.gz attached provides a small library to test this bug, so

    1) Build the library and get the introspection info by running make. 

    2) Run the test.sh script so it prepares the environment (search path for library and introspection) and runs the javascript test.js file.

Actual Results: 

    gjs outputs the following error:

    JS LOG: Command line: /usr/bin/gjs ./test.js
    JS ERROR: !!!   Exception was: Error: Can't create a Javascript object for ParamSpec; no way to copy
    JS ERROR: !!!     lineNumber = '0'
    JS ERROR: !!!     fileName = 'gjs_throw'
    JS ERROR: !!!     message = 'Can't create a Javascript object for ParamSpec; no way to copy'
    JS ERROR: !!!     stack = 'Error("Can't create a Javascript object for ParamSpec; no way to copy")@:0
("Can't create a Javascript object for ParamSpec; no way to copy")@gjs_throw:0
_private_GObject_ParamSpec()@:0
Error("Chained exception")@:0
("Chained exception")@gjs_throw:0
@:0
@./test.js:4
'
Error: Can't create a Javascript object for ParamSpec; no way to copy

Expected Results:

    gjs should be able to create a Javascript object for the GParamSpec type.

Build Date & Platform:

    gjs from git, commit id 324a06ee4bfc68ba13b4781d94f6f1d687c8b05c
    gobject-introspection from git, commit id b5270f2321640b5de52efc037aa0f76857fc67ad
    Built using jhbuild with gnome-3.0 moduleset.