3.5.5 Common Base Type

Given a set of multiple types, a common base type is a type which all types of the set unify against:

class Base {
  public function new() {}

class Child1 extends Base {}
class Child2 extends Base {}

class Main {
  static public function main() {
    var a = [new Child1(), new Child2()];
    $type(a); // Array<Base>

Although Base is not mentioned, the Haxe Compiler manages to infer it as the common type of Child1 and Child2. The Haxe Compiler employs this kind of unification in the following situations:

  • Array declarations.
  • if/else.
  • Cases of a switch.