Struct ScopeGuard

pub struct ScopeGuard<'a> { /* private fields */ }

A guard which allows “stashing” ElasticGuards for safe loaning.

Bare Elastic::loan is unsafe, because the returned ElasticGuard must be dropped. A ScopeGuard provided by ScopeArena::scope allows for collecting ElasticGuards through its safe ScopeGuard::loan method, because the ScopeArena ensures that all loans are ended at the end of the scope.

As an aside, ScopeGuard is an excellent example of a type which cannot be safely stretched: the lifetime parameter of the ScopeGuard corresponds to the accepted lifetime on the type parameter of ScopeGuard::loan. As a result, effectively, ScopeGuard has the variance of fn(&'a mut ...); it is safe to lengthen the lifetimes fed to ScopeGuard, but absolutely not safe to shorten them!

Implementations

impl<'a> ScopeGuard<'a>

pub fn loan<T: Stretchable<'a>>( &mut self, elastic: &Elastic<T::Stretched>, value: T, )

Loan to an elastic within the lifetime of the scope guard.

Trait Implementations

impl<'a> Debug for ScopeGuard<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.