Struct rust_examples::brands::InvariantLifetime

pub struct InvariantLifetime<'id>(_);

Lifetime wrapper which makes 'id invariant and has no size.

The invariance of 'id (resp. InvariantLifetime) comes from the underlying raw pointer type *mut &'id () - see the docs.

Zero size is achieved via the usage of opaque type PhantomData which only carries the type information until the compilation and then is “compiled away”.

Note that the invariance of 'id (resp. InvariantLifetime) means that one cannot change the brand ('id) of BrandedIndex or BrandedVec via subtyping.

Example: Size Test

use rust_examples::brands::InvariantLifetime;

assert_eq!(std::mem::size_of::<InvariantLifetime<'_>>(), std::mem::size_of::<()>());

Trait Implementations

impl<'id> Clone for InvariantLifetime<'id>

fn clone(&self) -> InvariantLifetime<'id>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'id> Default for InvariantLifetime<'id>

fn default() -> InvariantLifetime<'id>

Returns the “default value” for a type.

impl<'id> Copy for InvariantLifetime<'id>