avoid null Int issue on static targets

tests/unit/src/unit/issues/Issue3616.hx

@@ -1,6 +1,6 @@
 package unit.issues;
 
-private abstract A(Int) {
+private abstract A(Null<Int>) {
     public static function f(v:Int):Void {}
     public static function z():Void {}
 }
@@ -9,7 +9,7 @@ private abstract B<T>(T) {
     public static function f<T>(v:T):B<T> return cast v;
 }
 
-private abstract C(Int) {
+private abstract C(Null<Int>) {
     public static var f(get,set):Int;
     static function get_f() return 1;
     static function set_f(value) return 1;