Support more ways of inferring calling context #1239

class Foo {
  public function __construct() {
    if ($this instanceof Bar) {
      $this->bat(); // works
    }

    if (is_a($this, Bar::class)) {
      $this->bat(); // works
    }
	  
    if (is_a(static::class, Bar::class, true)) {
      $this->bat(); // fails
    }

    if (get_class($this) === Bar::class) {
      $this->bat(); // fails
    }

    if (static::class === Bar::class) {
      static::bat(); // fails
    }
  }
}

class Bar extends Foo {
  public static function bat() : void { }
}