The following code produces the warning "foobar.vala:11.3-11.7: warning: assigning to construct-only properties is deprecated, use Object (property: value) constructor chain up":

public class Foo : GLib.Object {
    public int a { get; construct; }
}

public class Bar : GLib.Object {
    private Foo foo;

    public Bar() {
        foo = new Foo();
        foo.a = 2;
    }
}

However it produces the following, invalid, C code ('self' is used before it is assigned to):

Bar* bar_construct (GType object_type) {
        GParameter * __params;
        GParameter * __params_it;
	Foo* _tmp0_;
	Bar * self;
        __params = g_new0 (GParameter, 1);
        __params_it = __params;
        self->priv->foo = (_tmp0_ = foo_new (), _g_object_unref0 (self->priv->foo), _tmp0_);
	__params_it->name = "a";
	g_value_init (&__params_it->value, G_TYPE_INT);
        g_value_set_int (&__params_it->value, 2);
        __params_it++;
        self = g_object_newv (object_type, __params_it - __params, __params);
        ...

My understanding of the 'construct' keyword is that the property should not be assigned to after the object has been created, thus the warning should actually be an error to prevent any code from being generated (and resulting in a segv crash at runtime).