[Vala] Type casting

[Hans Vercammen <hveso3 gmail com>]

Hi all,

First of all, many thanks for a great initiative which has in my opinion
a very bright future!

I am not quit sure on which level invalid type casts should be
monitored, whether it be the vala compiler or the underlaying gobject.
Please view the attached test-case for details.

As I understand, it should be possible to check incompatible types at
compile time and so eliminating further errors.

Regards,
Hans

using GLib;

public class Foo : Object {
	public int data { get; construct; }
	public Foo (construct int data) {
	}
}

public class FalseFoo : Object {

}

public class FooBar : Foo {
	public FooBar (int data) {
		this.data = data;
	}
}

public class App : Object {

	static int main (string[] args) {

		/* OK implitic cast is good */
		Foo foo = new FooBar (1);

		/* ERROR Should require explicit cast ? */
		FooBar foobar = new Foo (1);

		/* OK explicit cast required */
		foobar = (FooBar) foo;

		/* ERROR Should require explicit cast and fail on compatibility */
		Foo foo1 = new FalseFoo ();

		/* ERROR should fail on compatible type */
		FalseFoo falsefoo = (FalseFoo) foo;

		/* Silently accept null cast ? */
		foobar = null;
		foo = (Foo) foobar;

		/* Nullexception */
		foo.data = 5;

		/* OK foreach implicit upcast */
		foreach (Foo item in new FooBar[3]) {
		}

		/* ERROR should require explicit cast, not allowed in foreach */
		foreach (FooBar item in new Foo[3]) {
		}

		return 0;
	}
}