In both while break S {} {} and while return S {} {}, the value broken/returned is parsed as S {} by rustc, not just S. In other words whether or not allow_struct is true outside of the break/return expression, inside it's treated as true regardless.
In both
while break S {} {}andwhile return S {} {}, the value broken/returned is parsed asS {}by rustc, not justS. In other words whether or notallow_structis true outside of the break/return expression, inside it's treated as true regardless.