Please describe the problem:
Using Vala 3.3 I'm unable to use constants as properties default values. Trying to use constants as properties default values will result in an gcc error.

Steps to reproduce:

Try to compile that piece of code.

using GLib;

namespace Test {
	public const string TESTSTRING = "This is a Teststring.";


	public class FunWithConstants {

		public string test_string { public get; private set; default = "String"; }
	
	}
	
	public int main(string[] argv){
		return 0;
	}
	
	
}

Actual results:
Results in a gcc error: 

error.c: In function 'test_fun_with_constants_instance_init':
error.c:60: error: '_tmp0' undeclared (first use in this function)
error.c:60: error: (Each undeclared identifier is reported only once
error.c:60: error: for each function it appears in.)
error: cc exited with status 256
Compilation failed: 1 error(s), 0 warning(s)


Expected results:
Successful compilation.

Does this happen every time?
Yep.

Other information: