This code doesn't compile:

// delegate returning a function
public delegate Func<G> FuncGenerator<G> ();

void main () {
	FuncGenerator<int> func_generator = () => {
		return (data) => {
			print("hello %d!\n", data);
		};
	};
	Func<int> func = func_generator();
}

--------------------------------------------------

output:

/tmp/test.vala.QBFDCZ.c: In function ‘__lambda4_’:
/tmp/test.vala.QBFDCZ.c:36:9: warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]
  _tmp0_ = ___lambda5__gfunc;
         ^
/tmp/test.vala.QBFDCZ.c: In function ‘_vala_main’:
/tmp/test.vala.QBFDCZ.c:65:11: error: too few arguments to function ‘func_generator’
  _tmp1_ = func_generator (&_tmp0_, func_generator_target);
           ^~~~~~~~~~~~~~
error: cc exited with status 256