Re: [Vala] Invalid cast Warnings

[Luca Dionisi <luca dionisi gmail com>]

Obviously you can't cast an instance of a base class to a superclass.
You can do:
 var a = new TestSubType();
 TestBase b = (TestBase)a;

Not viceversa.


On Sun, Feb 5, 2017 at 6:30 PM, Al Thomas via vala-list
<vala-list gnome org> wrote:
> > ----- Original Message -----
>
> > From: Daniel Brendle <grindhold skarphed org>
> > Sent: Sunday, 5 February 2017, 16:09
> > Subject: [Vala] Invalid cast Warnings
>
> > At the moment I deal with a series of warnings like these:
>
> > (process:3325): GLib-GObject-WARNING **: invalid cast from 'OParlSystem'
> > to 'System'
>
> > I compiled a minimum example to trigger the issue here:
>
>
> > https://0bin.net/paste/J0sgx2b2NJp6lTj8#QBfz-GUhWagsfGsF7nUqEn/8XneAiL9NhYNIdo8GRt6
>
>
> A simpler example is:
>
> void main () {
>     var a = new TestBase ();
>     TestSubType b = (TestSubType)a;
> }
>
> class TestBase {
> }
>
> class TestSubType:TestBase {
> }
>
> The offending line in the resulting C code is:
>
> _tmp1_ = _test_base_ref0 (G_TYPE_CHECK_INSTANCE_CAST (a, TYPE_TEST_SUB_TYPE, TestSubType));
>
> It is G_TYPE_CHECK_INSTANCE_CAST (a, TYPE_TEST_SUB_TYPE, TestSubType) that is
> generating the warning.
>
>
> It needs further investigation as to why it's failing the check.
>
> Hopefully someone else will chip in with an answer.
>
> Al
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