Type safety

[petabyt]

Use C11 generics to add type safety to control type castings:

#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L

#undef uiControl
#undef uiButton

#define uiControl(this) _Generic((this), \
      uiControl *: this, \
      uiButton *: (uiControl *)this, \
      uiBox *: (uiControl *)this \
      )

#define uiButton(this) _Generic((this), \
      uiControl *: (uiButton *)this)

#endif

int main() {
    uiButton *btn = uiButton("Hello");
    uiControl(btn);
    uiControl("hello");
    return 0;
}