Function conjure_zst 

pub const unsafe fn conjure_zst<T>() -> T

🔬This is a nightly-only experimental API. (mem_conjure_zst #95383)

Create a fresh instance of the inhabited ZST type T.

Prefer this to zeroed or uninitialized or transmute_copy in places where you know that T is zero-sized, but don’t have a bound (such as Default) that would allow you to instantiate it using safe code.

If you’re not sure whether T is an inhabited ZST, then you should be using MaybeUninit, not this function.

Panics

If size_of::<T>() != 0.

Safety

• T must be inhabited, i.e. possible to construct. This means that types like zero-variant enums and ! are unsound to conjure.
• You must use the value only in ways which do not violate any safety invariants of the type.

While it’s easy to create a valid instance of an inhabited ZST, since having no bits in its representation means there’s only one possible value, that doesn’t mean that it’s always sound to do so.

For example, a library could design zero-sized tokens that are !Default + !Clone, limiting their creation to functions that initialize some state or establish a scope. Conjuring such a token could break invariants and lead to unsoundness.

Examples

#![feature(mem_conjure_zst)]
use std::mem::conjure_zst;

assert_eq!(unsafe { conjure_zst::<()>() }, ());
assert_eq!(unsafe { conjure_zst::<[i32; 0]>() }, []);