code: func ForceNewIf(key string, f ResourceConditionFunc) schema.CustomizeDiffFunc {
  	return func(d *schema.ResourceDiff, meta interface{}) error {
  		if f(d, meta) {
  			d.ForceNew(key)
  		}
  		return nil
  	}
  }
docs: // ForceNewIf returns a CustomizeDiffFunc that flags the given key as
  // requiring a new resource if the given condition function returns true.
  //
  // The return value of the condition function is ignored if the old and new
  // values of the field compare equal, since no attribute diff is generated in
  // that case.