If/else should have their own scopes

[lpereira]

The following program:

func bla(xxx interface{}) {
        if f, ok := xxx.(int); ok {
                println("xxx is int", f)
        } else {
                f := xxx.(Foo)
                println("xxx is not int, it's Foo:", f.bar)
        }
}

Will generate the following program:

void bla(moku::empty_interface xxx) {
  {
    int f{0};
    bool ok{false};

    std::tie(f, ok) = moku::try_type_assert<int>(xxx);

    if (ok) {
      println("xxx is int", f);
    } else {
      f = moku::type_assert<Foo>(xxx);
      println("xxx is not int, it's Foo:", f.bar);
    }
  }
}

The type of f in the else block is clearly wrong. The if and else blocks should have their own scopes.