Struct LifetimesMatterLittle 

pub struct LifetimesMatterLittle<T>(/* private fields */);

Marker that indicates that all lifetimes in T are just relevant for the type itself, but not for interactions. In particular, constructing it promises that:

• The type is covariant in all lifetimes: Any InputToT<'a> could be turned into an InputToT<'b> for a shorter 'b.

  In practice, this means that no public interfaces of the type take input that needs to outlive the type (e.g. some fn set_title(self, title: &'a str) { self.title = title }).

• It can not be observed through the type’s public interfaces how much longer its lifetime is than the reference that is passed in.

  In practice, this means that there can be a fn title(&self) -> &str, but no fn title(&self) -> &'a str.

Those properties are required to implement downcasting of generic messages into expected types, see Message::downcast_from().

In the type system, we can not convey information about incomplete types. Thus, the statement is encoded in a 'static concrete type T, but applies to the related types that vary by lifetimes.

Implementations

impl<T> LifetimesMatterLittle<T>

pub unsafe fn new() -> Self

Creates a new zero-sized marker.

Safety

This must only be used if T has the properties required by this type.